Phenytoin interactions

CYP3A4 Inducers: Avoid concomitant strong CYP3A4 inducers during YONSA treatment. (Abiraterone label, Drug interactions)

• CYP3A Inducers: Avoid co-administration with strong CYP3A inducers. (Acalabrutinib label, Drug interactions)

Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Acetaminophen and codeine label, Boxed warning)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

CYP3A4 Inducers : Avoid coadministration of VIJOICE with a strong CYP3A4 inducer. (Alpelisib label, Drug interactions)

• Effects on Driving and Operating Machinery: Patients receiving • alprazolam XR should be cautioned against operating machinery or driving a motor vehicle, as well as avoiding concomitant use of alcohol and other central nervous system (CNS) depressant drugs. (Alprazolam label, Warnings and precautions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

• Simultaneous use of combined P-gp and strong CYP3A4 inducers reduces blood levels of apixaban: Avoid concomitant use. (Apixaban label, Drug interactions)

Drug Interactions : Use with strong cytochrome P450 enzyme inducers (e.g., rifampin, phenobarbital, carbamazepine, phenytoin) is not recommended because loss of efficacy may occur ( 5.5 , 7.1 ) (Apremilast label, Warnings and precautions)

CYP3A4 Inducers : Avoid concomitant use for greater than 14 days ( 7.1 ) (Aripiprazole label, Drug interactions)

• when coadministered with drugs that are strong inducers of CYP3A due to the potential for loss of therapeutic effect and development of resistance. (Atazanavir label, Contraindications)

• Avoid concurrent use of alcohol or other central nervous system (CNS) depressants with azelastine hydrochloride and fluticasone propionate nasal spray because further decreased alertness and impairment of CNS performance may occur. (Azelastine and fluticasone label, Warnings and precautions)

…AND MISUSE; LIFE-THREATENING RESPIRATORY DEPRESSION; ACCIDENTAL EXPOSURE; NEONATAL OPIOD WITHDRAWAL SYNDROME; and RISKS FROM CONCOMITANT USE WITH ALCOHOL, BENZODIAZEPINES OR OTHER CNS DEPRESSANTS Addiction, Abuse, and Misuse Belladonna and opium suppositories expose patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to… (Belladonna and opium label, Boxed warning)

Concomitant administration of BIXLENVO is contraindicated with: dofetilide due to the potential for increased dofetilide plasma concentrations and associated serious and/or life-threatening events. strong CYP3A inducers due to decreased plasma concentrations of BIC and LEN, which may result in the loss of therapeutic effect and development of resistance to BIXLENVO. (Bictegravir, emtricitabine, and tenofovir alafenamide label, Contraindications)

…aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol… (Phenytoin label, Drug interactions)

Strong CYP3A4 Inducers: Avoid concomitant use. (Bortezomib label, Drug interactions)

• Strong CYP3A Inducers: Avoid concomitant use with BOSULIF. (Bosutinib label, Drug interactions)

Examples: Rifampin, carbamazepine, phenytoin Serotonergic Drugs Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. (Buprenorphine label, Drug interactions)

Bupropion hydrochloride extended-release tablets (XL) are contraindicated in patients undergoing abrupt discontinuation of alcohol, benzodiazepines, barbiturates, and antiepileptic drugs [see Warnings and Precautions (5.3) and Drug Interactions (7.3)] . (Bupropion label, Contraindications)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Butalbital, acetaminophen, caffeine, and codeine label, Boxed warning)

Concomitant use of opioids or a barbiturate with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Butalbital, aspirin, caffeine, and codeine label, Boxed warning)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Butorphanol label, Boxed warning)

• Coadministration with carbamazepine, oxcarbazepine, phenobarbital, phenytoin, rifampin, and rifapentine. (Cabotegravir label, Contraindications)

Avoid chronic co-administration of strong CYP3A4 inducers (e.g., phenytoin, carbamazepine, rifampin, rifabutin, rifapentine, phenobarbital, St. (Cabozantinib label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Consider avoiding phenytoin as an alternative to carbamazepine in patients who are positive for HLA-B*1502 or in CYP2C9*3 carriers [see Use in Specific Populations (8.7) and Clinical Pharmacology (12.5) ] . (Phenytoin label, Warnings and precautions)

Avoid concurrent use of Carbinoxamine Maleate Extended-Release Oral Suspension with alcohol or other central nervous system depressants because additional impairment of central nervous system performance may occur. (Carbinoxamine label, Warnings and precautions)

…hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam,… (Phenytoin label, Drug interactions)

Intervention: Concomitant use of VRAYLAR with a CYP3A4 inducer is not recommended [see Dosage and Administration ( 2.1 , 2.6 ) ] . (Cariprazine label, Drug interactions)

Avoid concurrent use of QUZYTTIR with alcohol or other CNS depressants because additional reduction in alertness and additional impairment of CNS performance may occur. (Cetirizine label, Warnings and precautions)

Phenytoin Use with caution Altered serum levels of phenytoin (increased and decreased) To avoid the loss of seizure control associated with decreased phenytoin levels and to prevent phenytoin overdose-related adverse reactions upon ciprofloxacin discontinuation in patients receiving both agents, monitor phenytoin therapy, including phenytoin serum concentration… (Ciprofloxacin label, Drug interactions)

…magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide,… (Phenytoin label, Drug interactions)

Avoid use with other central nervous system (CNS) depressants ( 5.3 ) (Clonidine label, Warnings and precautions)

• Concomitant use of Strong CYP3A4 Inducers is not recommended. (Clozapine label, Drug interactions)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Codeine label, Boxed warning)

Based on its structural similarity to TCAs, concomitant use of TONMYA with: MAO inhibitors may be life-threatening [see Contraindications (4) ] , Alcohol, barbiturates, and other CNS depressants may increase the risk of adverse reactions associated with these drugs, Tramadol may increase the seizure risk, Guanethidine or other similar acting drugs may block the… (Cyclobenzaprine label, Drug interactions)

Moderate or Strong CYP3A4 inducers: Avoid concomitant use. (Daridorexant label, Drug interactions)

…elbasvir/grazoprevir Lipid modifying agents: lomitapide, lovastatin, simvastatin Opioid Antagonist: naloxegol PDE-5 inhibitor: sildenafil when used for treatment of pulmonary arterial hypertension Sedatives/hypnotics: orally administered midazolam, triazolam Co-administration of PREZISTA/ritonavir is contraindicated with drugs that are highly dependent on CYP3A for clearance… (Darunavir label, Contraindications)

Co-administration of PREZCOBIX or PREZCOBIX PED with CYP3A inducers may lead to lower exposures of darunavir and cobicistat and potential loss of efficacy of darunavir and possible resistance. (Darunavir and cobicistat label, Contraindications)

If concomitant administration of a strong CYP3A4 inducer cannot be avoided, consider a dose increase [see Dosage and Administration ( 2.3 )] . (Dasatinib label, Drug interactions)

Avoid use of moderate or strong CYP3A4 inducers with EMFLAZA, as they may reduce efficacy ( 7.1 ) (Deflazacort label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

CONTRAINDICATIONS Diphenoxylate hydrochloride and atropine sulfate is contraindicated in: • Pediatric patients less than 6 years of age due to the risks of respiratory and central nervous system (CNS) depression (see WARNINGS ). (Diphenoxylate and atropine label, Contraindications)

Children under the age of two years are at a considerably increased risk of developing fatal hepatotoxicity, especially those on multiple anticonvulsants, those with congenital metabolic disorders, those with severe seizure disorders accompanied by mental retardation, and those with organic brain disease. (Divalproex (valproate) label, Boxed warning)

PIFELTRO is contraindicated when co-administered with drugs that are strong cytochrome P450 (CYP)3A enzyme inducers as significant decreases in doravirine plasma concentrations may occur, which may decrease the effectiveness of PIFELTRO [see Warnings and Precautions (5.2) , Drug Interactions (7.1) , and Clinical Pharmacology (12.3) ] . (Doravirine label, Contraindications)

…hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic… (Phenytoin label, Drug interactions)

• CYP3A inducers: Avoid concomitant use. (Dronedarone label, Drug interactions)

Therefore, concomitant use with strong CYP3A inducers is not recommended [see Drug Interactions (7.1) and Clinical Pharmacology (12.3) ] . (Elexacaftor, tezacaftor, and ivacaftor label, Warnings and precautions)

Alpha 1-adrenoreceptor antagonist: alfuzosin Anticonvulsants: carbamazepine, phenobarbital, phenytoin Antimycobacterial: rifampin Antipsychotics: lurasidone, pimozide Ergot Derivatives: dihydroergotamine, ergotamine, methylergonovine Herbal Products: St. (Elvitegravir, cobicistat, emtricitabine, and tenofovir label, Contraindications)

…virologic response and possible resistance to COMPLERA or to the class of NNRTIs [see Warnings and Precautions (5.7) , Drug Interactions (7) , and Clinical Pharmacology (12.3) ]: Anticonvulsants: carbamazepine, oxcarbazepine, phenobarbital, phenytoin Antimycobacterials: rifampin, rifapentine Glucocorticoid (systemic): dexamethasone (more than a single-dose)… (Emtricitabine, rilpivirine, and tenofovir label, Contraindications)

Avoid smoking tobacco (CYP1A2 inducer) and avoid concomitant use of erlotinib with moderate CYP1A2 inducers (e.g., teriflunomide, rifampin, or phenytoin). (Erlotinib label, Drug interactions)

The use of LUNESTA with other sedative-hypnotics at bedtime or the middle of the night is not recommended. (Eszopiclone label, Warnings and precautions)

Etravirine should not be used in combination with carbamazepine, phenobarbital, or phenytoin as co-administration may cause significant decreases in etravirine plasma concentrations and loss of therapeutic effect of Etravirine. (Etravirine label, Drug interactions)

IT IS NOT KNOWN WHETHER CONCOMITANT USE OF OTHER ANTIEPILEPTIC DRUGS AND/OR OTHER DRUGS AFFECT THE INCIDENCE OF HEPATIC FAILURE. (Felbamate label, Boxed warning)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

• Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Fentanyl label, Boxed warning)

Preventing or Managing DI The concomitant use of ADDYI with CYP3A4 inducers is not recommended. (Flibanserin label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

Intervention Avoid concomitant use of FOCINVEZ Examples rifampin, carbamazepine, phenytoin (Fosaprepitant label, Drug interactions)

WARNING: CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION RATES The rate of intravenous CEREBYX administration should not exceed 150 mg phenytoin sodium equivalents (PE) per minute in adults and 2 mg PE/kg/min (or 150 mg PE/min, whichever is slower) in pediatric patients because of the risk of severe hypotension and cardiac arrhythmias. (Fosphenytoin label, Boxed warning)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Hydrocodone label, Boxed warning)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Hydrocodone and acetaminophen label, Boxed warning)

Phenytoin : Avoid concomitant use; may increase phenytoin levels. (Hydrocodone and chlorpheniramine label, Drug interactions)

…ABUSE, AND MISUSE; LIFE-THREATENING RESPIRATORY DEPRESSION; ACCIDENTAL INGESTION; MEDICATION ERRORS; CYTOCHROME P450 3A4 INTERACTION; CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS; INTERACTION WITH ALCOHOL; NEONATAL OPIOID WITHDRAWAL SYNDROME Addiction, Abuse, and Misuse Hydrocodone bitartrate and homatropine methylbromide exposes patients and… (Hydrocodone and homatropine label, Boxed warning)

…LIFE-THREATENING RESPIRATORY DEPRESSION; ACCIDENTAL INGESTION; NEONATAL OPIOID WITHDRAWAL SYNDROME; CYTOCHROME P4503A4 INTERACTION; RISKS FROM CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS; and SERIOUS CARDIOVASCULAR AND GASTROINTESTINAL EVENTS WARNING: SERIOUS AND LIFE-THREATENING RISKS FROM USE OF HYDROCODONE BITARTRATE AND IBUPROFEN TABLETS Addiction,… (Hydrocodone and ibuprofen label, Boxed warning)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death . (Hydromorphone label, Boxed warning)

Rarely, cardiac arrests and death have been reported in association with the combined use of hydroxyzine hydrochloride intramuscularly and other CNS depressants. (Hydroxyzine label, Precautions)

• Strong CYP3A4 Inducers: Do not administer strong CYP3A4 inducers with CAMPTOSAR. (Irinotecan label, Drug interactions)

To avoid phenytoin intoxication, appropriate adjustment of the anticonvulsant should be made 5,6 . (Isoniazid label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Anticonvulsants Carbamazepine Not recommended 2 weeks before, during, and 2 weeks after TOLSURA treatment. (Itraconazole label, Drug interactions)

Avoid concomitant use of CYP3A4 inducers when using Corlanor. (Ivabradine label, Drug interactions)

Benzodiazepines, Opioid Analgesics, or other CNS Depressants : Concomitant use may result in profound sedation, respiratory depression, coma, or death. (Ketamine label, Drug interactions)

This may potentiate and prolong hypnotic and sedative effects, especially with repeated dosing or chronic administration of these agents. (Ketoconazole label, Contraindications)

Avoid strong CYP3A4 inducers. (Lapatinib label, Drug interactions)

Strong CYP3A4 Inducers: Avoid coadministration of strong CYP3A4 inducers with VITRAKVI. (Larotrectinib label, Drug interactions)

Strong or moderate CYP3A inducers: Avoid concomitant use. (Lemborexant label, Drug interactions)

Concomitant administration of SUNLENCA with carbamazepine or phenytoin is contraindicated. (Lenacapavir label, Drug interactions)

Avoid concurrent use of alcohol or other central nervous system depressants with XYZAL. (Levocetirizine label, Warnings and precautions)

Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Levorphanol label, Boxed warning)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

Caution patients receiving LOREEV XR against operating machinery or driving a motor vehicle as well to avoid the concomitant use of alcohol and other CNS depressant drugs during treatment ( 5.4 , 7 ) (Lorazepam label, Warnings and precautions)

Effect of Other Drugs on LORBRENA Strong CYP3A Inducers LORBRENA is contraindicated in patients taking strong CYP3A inducers [see Contraindication (4) ] . (Lorlatinib label, Drug interactions)

CYP3A4 inducers: Avoid concomitant use with CAPLYTA. (Lumateperone label, Drug interactions)

John's wort, phenytoin, carbamazepine, etc.) [see Drug Interactions ( 7.1 )]. (Lurasidone label, Contraindications)

Strong CYP3A4 inducers (rifampin) reduce exposure to macitentan: avoid co-administration with OPSUMIT ( 7.1 , 12.3 ). (Macitentan label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Meperidine label, Boxed warning)

If concomitant use with another CNS depressant is warranted, closely monitor for signs of respiratory depression and sedation, particularly during treatment initiation and dosage increases. (Metaxalone label, Warnings and precautions)

Managing Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants Concomitant use with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, is a risk factor for respiratory depression and death [see Warnings and Precautions ( 5.2 )]. (Methadone label, Boxed warning)

…Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine,… (Phenytoin label, Drug interactions)

WARNING: PERSONNEL AND EQUIPMENT FOR MONITORING AND RESUSCITATION AND RISKS FROM CONCOMITANT USE WITH OPIOID ANALGESICS AND OTHER SEDATIVE-HYPNOTICS Personnel and Equipment for Monitoring and Resuscitation Only personnel trained in the administration of procedural sedation, and not involved in the conduct of the diagnostic or therapeutic procedure, should administer… (Midazolam label, Boxed warning)

CYP3A inducers: Do not use mifepristone with CYP3A inducers ( 7.3 ). (Mifepristone label, Drug interactions)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Morphine label, Boxed warning)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Nalbuphine label, Boxed warning)

John's Wort) Clinical Impact Significant decrease in plasma naldemedine concentrations, which may reduce efficacy [see Clinical Pharmacology (12.3) ] Intervention Avoid use of SYMPROIC with strong CYP3A inducers. (Naldemedine label, Drug interactions)

Risk of Recurrent Respiratory and CNS Depression : A recurrence of respiratory depression is possible, therefore, keep the patient under continued surveillance and administer repeat doses of ZURNAI using a new auto-injector with each dose while awaiting emergency medical assistance. (Nalmefene label, Warnings and precautions)

Strong CYP3A4 inducers (e.g., rifampin) : Decreased concentrations of naloxegol; concomitant use is not recommended. (Naloxegol label, Drug interactions)

CYP2B6 Inducers (e.g., ritonavir, lopinavir, efavirenz, carbamazepine, phenobarbital, and phenytoin) may reduce efficacy by reducing bupropion exposure, avoid concomitant use. (Naltrexone and bupropion label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Strong CYP3A Inducers: Avoid concomitant use with CAVHANZA. (Nilotinib label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Counsel patients to use a back-up method or alternative method of contraception when enzyme inducers are used with COCs ( 7.1 ) -- - ---------- ------ USE IN SPECIFIC POPULATIONS---- -- -- --------- ---- Lactation: Not recommended; Lo Loestrin Fe can decrease milk production ( 8.2 ) (Norethindrone and ethinyl estradiol label, Drug interactions)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Oliceridine label, Boxed warning)

• Avoid concurrent use of alcohol or other central nervous system depressants with olopatadine hydrochloride nasal solution (nasal spray) ( 5.2 ). (Olopatadine label, Warnings and precautions)

• Avoid concurrent use of alcohol or other central nervous system (CNS) depressants with RYALTRIS because additional reductions in alertness and additional impairment of CNS performance may occur. (Olopatadine and mometasone label, Warnings and precautions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Oxycodone label, Boxed warning)

…LIFE-THREATENING RESPIRATORY DEPRESSION; ACCIDENTAL INGESTION; NEONATAL OPIOID WITHDRAWAL SYNDROME; CYTOCHROME P450 3A4 INTERACTION; and RISKS FROM CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS Addiction, Abuse, and Misuse Oxycodone hydrochloride tablets exposes patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to… (Oxycodone and acetaminophen label, Boxed warning)

Risks From Concomitant Use with Benzodiazepines or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Oxymorphone label, Boxed warning)

• CYP3A Inducers: Avoid concurrent use of IBRANCE with strong CYP3A inducers. (Palbociclib label, Drug interactions)

Strong CYP3A4 and P-glycoprotein (P-gp) inducers : Avoid using a strong inducer of CYP3A4 and/or P-gp during a dosing interval for ERZOFRI. (Paliperidone label, Drug interactions)

VOTRIENT is not recommended if chronic use of strong CYP3A4 inducers cannot be avoided. (Pazopanib label, Drug interactions)

…MITIGATION STRATEGY (REMS); LIFE-THREATENING RESPIRATORY DEPRESSION; ACCIDENTAL INGESTION; NEONATAL OPIOID WITHDRAWAL SYNDROME; and RISKS FROM CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS Addiction, Abuse, and Misuse Pentazocine and Naloxone Tablets exposes patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to… (Pentazocine and naloxone label, Boxed warning)

Phenelzine sulfate should not be used in combination with dextromethorphan or with CNS depressants such as alcohol and certain narcotics. (Phenelzine label, Contraindications)

A potentially life-threatening bleeding disorder related to decreased levels of vitamin K-dependent clotting factors may occur in newborns exposed to phenytoin in utero. (Phenytoin label, Warnings and precautions)

Strong or Moderate CYP3A4 Inducers: Avoid concomitant use of NUPLAZID. (Pimavanserin label, Drug interactions)

Phenytoin Avoid concomitant use of posaconazole with phenytoin unless the benefit to the patient outweighs the risk. (Posaconazole label, Drug interactions)

• Patients taking strong Cytochrome P450 3A enzyme (CYP3A) inducers, such as rifampin, [see Warnings and Precautions ( 5.6 ) and Drug Interactions ( 7.1 , 7.2 )] . (Praziquantel label, Contraindications)

…PROMETHAZINE AND RESPIRATORY DEPRESSION IN CHILDREN; MEDICATION ERRORS; INTERACTIONS WITH DRUGS AFFECTING CYTOCHROME P450 ISOENZYMES; CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS; NEONATAL OPIOID WITHDRAWAL SYNDROME Addiction, Abuse, and Misuse Promethazine HCl and Codeine Phosphate Oral Solution exposes patients and other users to the risks… (Promethazine and codeine label, Boxed warning)

If concomitant administration with carbamazepine or phenobarbital cannot be avoided, frequent monitoring of anticonvulsant drug concentrations is recommended. (Quinine label, Drug interactions)

ASPRUZYO Sprinkle is contraindicated in patients: Taking strong inhibitors of CYP3A [see Drug Interactions (7.1)] Taking inducers of CYP3A [see Drug Interactions (7.1)] With liver cirrhosis [see Use in Specific Populations (8.6)] Strong CYP3A inhibitors (e.g., ketoconazole, clarithromycin, nelfinavir) (4, 7.1) (Ranolazine label, Contraindications)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Remifentanil label, Boxed warning)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

Table 2: Drugs That are Contraindicated with EDURANT and EDURANT PED Drug Class Contraindicated Drugs in Class Clinical Comment Anticonvulsants Carbamazepine Oxcarbazepine Phenobarbital Phenytoin Potential for significant decreases in rilpivirine plasma concentrations due to CYP3A enzyme induction, which may result in loss of virologic response. (Rilpivirine label, Contraindications)

• Strong and Moderate CYP3A Inducers: Avoid concomitant administration. (Rimegepant label, Drug interactions)

• Certain CYP3A inducers: Coadministration with strong inducers of CYP3A is not recommended. (Ritlecitinib label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

Avoid concomitant use of XARELTO with drugs that are known combined P-gp and strong CYP3A inducers [see Drug Interactions (7.3) ] . (Rivaroxaban label, Warnings and precautions)

Therefore the use of strong cytochrome P450 inducers (e.g., rifampicin, phenobarbital, carbamazepine, and phenytoin) with DALIRESP is not recommended [see Warnings and Precautions (5.4) and Clinical Pharmacology (12.3) ]. (Roflumilast label, Drug interactions)

Intervention: Avoid the use of VARUBI in patients who require chronic administration of strong CYP3A4 inducers. (Rolapitant label, Drug interactions)

• Avoid use with rifampin and strong CYP3A4 inducers ( 7.3 ). (Romidepsin label, Drug interactions)

Interaction with Strong Inhibitors and Inducers of CYP3A4 and/or P-gp Avoid concomitant use of sirolimus with strong inhibitors of CYP3A4 and/or P-gp (such as ketoconazole, voriconazole, itraconazole, erythromycin, telithromycin, or clarithromycin) or strong inducers of CYP3A4 and/or P-gp (such as rifampin or rifabutin) [ see Drug Interactions (7.2) ]. (Sirolimus label, Warnings and precautions)

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management: Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other… (Phenytoin label, Drug interactions)

Abuse or misuse of illicit GHB, either alone or in combination with other CNS depressants, is associated with CNS adverse reactions, including seizure, respiratory depression, decreases in the level of consciousness, coma, and death [see Warnings and Precautions ( 5.2 )]. (Sodium oxybate label, Boxed warning)

Anticonvulsants: carbamazepine phenytoin phenobarbital ↓ sofosbuvir ↓ velpatasvir ↓ voxilaprevir Coadministration is not recommended. (Sofosbuvir and velpatasvir label, Drug interactions)

• Strong CYP3A Inducers: Avoid strong CYP3A4 inducers. (Sorafenib label, Drug interactions)

Inducers of CYP3A4 Strong CYP3A4 inducers should not be used with tamoxifen. (Tamoxifen label, Drug interactions)

Risks From Concomitant Use With Benzodiazepines Or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Tapentadol label, Boxed warning)

Strong CYP3A4 inducers (e.g., rifampin): Avoid use of HETLIOZ in combination with rifampin or other CYP3A4 inducers, because of decreased exposure ( 7.2 , 12.3 ) (Tasimelteon label, Drug interactions)

Avoid co-administration of strong CYP3A4 inhibitors (e.g., itraconazole, clarithromycin, ritonavir) and strong CYP3A4 inducers (e.g., rifampin, phenytoin) with TEPADINA due to the potential effects on efficacy and toxicity [see Clinical Pharmacology ( 12.3 ) ] . (Thiotepa label, Drug interactions)

• Avoid use with strong CYP3A inhibitors or CYP3A inducers. (Ticagrelor label, Drug interactions)

Avoid concomitant use of SAMSCA with strong CYP3A inducers. (Tolvaptan label, Drug interactions)

Coadministration with a strong CYP3A4 inducer may result in a relevant decrease in FARESTON exposure and should be avoided. (Toremifene label, Drug interactions)

CYP3A inducers: Avoid concomitant strong CYP3A inducers ( 7.1 ) (Trabectedin label, Drug interactions)

Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Tramadol label, Boxed warning)

Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants Concomitant use of opioids with benzodiazepines or other central nervous system (CNS) depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death. (Tramadol and acetaminophen label, Boxed warning)

Avoid concomitant use with strong CYP3A inducers if possible. (Tretinoin label, Drug interactions)

• Effects on Driving and Operating Heavy Machinery : Patients receiving triazolam should be cautioned against driving or operating heavy machinery, as well as avoiding concomitant use with alcohol and other CNS depressant drugs. (Triazolam label, Warnings and precautions)

Strong CYP3A4 Inducers: Should be avoided as concomitant use will result in reduction of ubrogepant exposure. (Ubrogepant label, Drug interactions)

Avoid co-administration of ella and drugs or herbal products such as: • barbiturates • bosentan • carbamazepine • felbamate • griseofulvin • oxcarbazepine • phenytoin • rifampin • St. (Ulipristal label, Drug interactions)

Strong CYP3A4 Inducers : Coadministration of RINVOQ/RINVOQ LQ with strong CYP3A4 inducers is not recommended. (Upadacitinib label, Drug interactions)

Use of strong CYP3A4 inducers with INGREZZA or INGREZZA SPRINKLE Concomitant use is not recommended. (Valbenazine label, Drug interactions)

Children under the age of two years are at a considerably increased risk of developing fatal hepatotoxicity, especially those on multiple anticonvulsants, those with congenital metabolic disorders, those with severe seizure disorders accompanied by mental retardation, and those with organic brain disease. (Valproic acid label, Boxed warning)

Strong CYP3A Inducers : Avoid concomitant use with strong CYP3A inducers. (Vepdegestrant label, Drug interactions)

…Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents (usually in combination) Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. (Phenytoin label, Drug interactions)

A potentially life-threatening bleeding disorder related to decreased levels of vitamin K-dependent clotting factors may occur in newborns exposed to phenytoin in utero. (Phenytoin label, Warnings and precautions)

…Contraindicated Long Acting Barbiturates (e.g., phenobarbital, mephobarbital) (CYP450 Induction) Not Studied In Vivo or In Vitro , but Likely to Result in Significant Reduction Contraindicated Phenytoin (CYP450 Induction) Significantly Reduced Increase voriconazole maintenance dose from 4 mg/kg to 5 mg/kg IV every 12 hours or from 200 mg to 400 mg orally every 12 hours (100… (Voriconazole label, Drug interactions)

The use of zaleplon with other sedative-hypnotics at bedtime or the middle of the night is not recommended (see ). (Zaleplon label, Warnings)

The use of Zolpidem Tartrate with other sedative-hypnotics (including other zolpidem products) at bedtime or the middle of the night is not recommended. (Zolpidem label, Warnings and precautions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

Phenytoin: If acitretin is given concurrently with phenytoin, the protein binding of phenytoin may be reduced. (Acitretin label, Drug interactions)

…given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine 7.3 Hyperammonemia… (Phenytoin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

Examples: Thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs and isoniazid Alogliptin Cytochrome (CYP) P450, CYP-Substrates or Inhibitors Clinical Impact: Insulin Secretagogues and Insulin Insulin and insulin secretagogues… (Alogliptin and metformin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

…acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

Effects of NUVIGIL on CYP2C19 Substrates Elimination of drugs that are substrates for CYP2C19 (e.g., phenytoin, diazepam, propranolol, omeprazole, and clomipramine) may be prolonged by NUVIGIL via inhibition of metabolic enzymes, with resultant higher systemic exposure. (Armodafinil label, Drug interactions)

…cyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicase Antibiotics dapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamides Antimalarials chloroquine, primaquine Anticonvulsants phenobarbital, phenytoin, sodium valproate Other drugs acetaminophen, metoclopramide, quinine, sulfasalazine Monoamine Oxidase Inhibitors, Nonselective Beta-Adrenergic… (Articaine and epinephrine label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Drug Interactions: In a single patient-report, there is the suggestion that concurrent administration of Auranofin Capsules and phenytoin may have increased phenytoin blood levels. (Auranofin label, Drug interactions)

CYP3A4/5 Inducers Co-administration of rifampin, a strong inducer of CYP3A4/5, reduced the plasma exposure of axitinib in healthy volunteers. (Axitinib label, Drug interactions)

Until further data are developed regarding drug interactions when digoxin, colchicine or phenytoin are used with azithromycin careful monitoring of patients is advised. (Azithromycin label, Drug interactions)

Patients should also be cautioned that the central nervous system depressant effects of intrathecal baclofen may be additive to those of alcohol and other CNS depressants. (Baclofen label, Warnings and precautions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Clinically Significant Interactions with Bexagliflozin Tablets UGT Enzyme Inducers Clinical Impact UGT Enzyme Inducers may significantly reduce exposure to bexagliflozin and lead to a decreased efficacy [ see Clinical Pharmacology ( 12.3 )]. (Bexagliflozin label, Drug interactions)

Inducers of CYP450 liver enzymes The simultaneous administration of bismuth subcitrate potassium, metronidazole and tetracycline hydrochloride and drugs that induce microsomal liver enzymes, such as phenytoin or phenobarbital, may accelerate the elimination of metronidazole, resulting in reduced plasma concentrations of metronidazole. (Bismuth subcitrate, metronidazole, and tetracycline label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

Strong CYP3A4 inducers Double the recommended dosage and further adjust based on clinical response. (Brexpiprazole label, Drug interactions)

Use with CNS depressants may result in an additive or potentiating effect. (Brimonidine label, Drug interactions)

Use with CNS depressants may result in an additive or potentiating effect. (Brimonidine and timolol label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Therefore, potent inhibitors or inducers of CYP3A4 may increase or reduce the circulating levels of CYCLOSET, respectively. (Bromocriptine label, Drug interactions)

Central Nervous System (CNS) depressants Antihistamines have additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, antianxiety agents, etc.). Antihypertensive drugs Sympathomimetic may reduce the effects of antihypertensive drugs. (Brompheniramine, pseudoephedrine, and dextromethorphan label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Possible early warning signs of central nervous system (CNS) toxicity are restlessness, anxiety, incoherent speech, lightheadedness, numbness and tingling of the mouth and lips, metallic taste, tinnitus, dizziness, blurred vision, tremors, twitching, CNS depression, or drowsiness. (Bupivacaine label, Warnings and precautions)

Possible early warning signs of central nervous system (CNS) toxicity are restlessness, anxiety, incoherent speech, lightheadedness, numbness and tingling of the mouth and lips, metallic taste, tinnitus, dizziness, blurred vision, tremors, twitching, CNS depression, or drowsiness. (Bupivacaine and epinephrine label, Warnings and precautions)

Warn patients of the potential danger of self-administration of benzodiazepines or other CNS depressants while under treatment with buprenorphine and naloxone sublingual tablets [see Warnings and Precautions (5.3) , Drug Interactions (7) ] . (Buprenorphine and naloxone label, Warnings and precautions)

Triazolam/flurazepam: Coadministration of buspirone with either triazolam or flurazepam did not appear to prolong or intensify the sedative effects of either benzodiazepine. (Buspirone label, Drug interactions)

Additionally, consider alternatives to structurally similar drugs such as carboxamides (e.g., carbamazepine), barbiturates, succinimides, and oxazolidinediones (e.g., trimethadione) in these same patients. (Phenytoin label, Warnings and precautions)

Additionally, consider alternatives to structurally similar drugs such as carboxamides (e.g., carbamazepine), barbiturates, succinimides, and oxazolidinediones (e.g., trimethadione) in these same patients. (Phenytoin label, Warnings and precautions)

Additionally, consider alternatives to structurally similar drugs such as carboxamides (e.g., carbamazepine), barbiturates, succinimides, and oxazolidinediones (e.g., trimethadione) in these same patients. (Phenytoin label, Warnings and precautions)

Effects on Vitamin D and Bone The chronic use of phenytoin in patients with epilepsy has been associated with decreased bone mineral density (osteopenia, osteoporosis, and osteomalacia) and bone fractures. (Phenytoin label, Warnings and precautions)

Effects on Vitamin D and Bone The chronic use of phenytoin in patients with epilepsy has been associated with decreased bone mineral density (osteopenia, osteoporosis, and osteomalacia) and bone fractures. (Phenytoin label, Warnings and precautions)

Examples: Rifampin, phenytoin, phenobarbital, ritonavir Insulin or Insulin Secretagogues Clinical Impact: The risk of hypoglycemia is increased when INVOKANA is used concomitantly with insulin secretagogues (e.g., sulfonylurea) or insulin. (Canagliflozin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

…Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole,… (Phenytoin label, Drug interactions)

• Dopamine D2 receptor antagonists, isoniazid, phenytoin, papaverine and iron salts: may reduce efficacy of Carbidopa, levodopa and entacapone tablets ( 7.5 , 7.6 , 7.7 , 7.8 , 7.9 ) • Drugs that interfere with biliary excretion, glucuronidation and intestinal beta-glucuronidase: dose adjustment of Carbidopa, levodopa and entacapone tablets may be required (… (Carbidopa, levodopa, and entacapone label, Drug interactions)

• Additive sedative effects when used with other CNS depressants including alcohol (5.1) (Carisoprodol label, Warnings and precautions)

Phenytoin: Carmustine for Injection may reduce the efficacy of phenytoin. (Carmustine label, Drug interactions)

…Hepatic CYP Enzymes Adults : When Caspofungin acetate for Injection is co-administered to adult patients with other inducers of hepatic CYP enzymes, such as efavirenz, nevirapine, phenytoin, dexamethasone, or carbamazepine, administration of a daily dose of 70 mg of Caspofungin acetate for Injection should be considered [see Dosage and Administration ( 2.5 )… (Caspofungin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

…antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin… (Phenytoin label, Drug interactions)

…antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin… (Phenytoin label, Drug interactions)

…procaine, ropivacaine, tetracaine Antineoplastic agents cyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicase Antibiotics dapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamides Antimalarials chloroquine, primaquine Anticonvulsants Phenobarbital, phenytoin, sodium valproate Other drugs acetaminophen, metoclopramide, quinine, sulfasalazine (Chloroprocaine label, Precautions)

However, it has been reported that chlorpromazine may interfere with the metabolism of phenytoin and thus precipitate phenytoin toxicity. (Chlorpromazine label, Precautions)

Chlorzoxazone use should also be discontinued if a patient develops abnormal liver enzymes (e.g., AST, ALT, alkaline phosphatase and bilirubin.) The concomitant use of alcohol or other central nervous system depressants may have an additive effect. (Chlorzoxazone label, Warnings and precautions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

…Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone,… (Phenytoin label, Drug interactions)

Antibiotics † Local anesthetics Magnesium salts Procainamide Lithium Quinidine May prolong the neuromuscular blockade action of Cisatracurium Besylate Injection Phenytoin, Carbamazepine May increase resistance to the neuromuscular blockade action of Cisatracurium Besylate Injection resulting in shorter durations of neuromuscular blockade and infusion rate requirements… (Cisatracurium label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Other Drugs Metabolized by CYP450 Isoforms Other than CYP3A: Hexobarbital Phenytoin Valproate Use With Caution There have been postmarketing reports of interactions of clarithromycin with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate. (Clarithromycin label, Drug interactions)

Use with CNS Depressants Clemastine has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc.). Use in Activities Requiring Mental Alertness Patients should be warned about engaging in activities requiring mental alertness such as driving a car or operating appliances, machinery, etc. (Clemastine label, Warnings)

Inducers of CYP3A4 and CYP3A5 Inducers of CYP3A4 and/or CYP3A5 may reduce plasma concentrations of clindamycin. (Clindamycin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. (Clorazepate label, Warnings)

…Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric… (Phenytoin label, Drug interactions)

Concomitant use with colesevelam hydrochloride may decrease the exposure of the following drugs: Drugs with a narrow therapeutic index (e.g., cyclosporine), phenytoin, thyroid hormone replacement therapy, warfarin, oral contraceptives containing ethinyl estradiol and norethindrone, olmesartan medoxomil, and sulfonylureas (glimepiride, glipizide, glyburide). (Colesevelam label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine 7.3 Hyperammonemia with Concomitant Use of Valproate Concomitant administration of phenytoin… (Phenytoin label, Drug interactions)

CNS Depressants Antihistamines may have additive effects with alcohol and other CNS depressants, e.g., hypnotics, sedatives, tranquilizers, antianxiety agents. (Cyproheptadine label, Warnings)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

The concomitant use of Exjade with potent UGT inducers (e.g., rifampicin, phenytoin, phenobarbital, ritonavir) may result in a decrease in Exjade efficacy due to a possible decrease in deferasirox concentration. (Deferasirox label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Alcohol or other sedating drugs: May have additive sedation and somnolence ( 7.5 ) (Deutetrabenazine label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Use with CNS Depressants CORPHENA Oral Solution has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc.). Use in Activities Requiring Mental Alertness Patients should be warned about engaging in activities requiring mental alertness such as driving a car or operating appliances, machinery, etc. (Dexchlorpheniramine label, Warnings)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

…decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs… (Phenytoin label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

Exercise caution when prescribing ZIPSOR with concomitant drugs that are known to be potentially hepatotoxic (e.g., acetaminophen, antibiotics, antiepileptics). (Diclofenac label, Warnings and precautions)

Exercise caution when prescribing diclofenac sodium/misoprostol with concomitant drugs that are known to be potentially hepatotoxic (e.g., antibiotics, anti-epileptics). (Diclofenac and misoprostol label, Warnings and precautions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

…concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine 7.3 Hyperammonemia with Concomitant Use of Valproate Concomitant administration of phenytoin and valproate… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

The concomitant use of alcohol or other central nervous system depressants may have an additive effect. (Dimenhydrinate label, Warnings)

Drug Interactions Diphenhydramine hydrochloride has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc). (Diphenhydramine label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

…amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine 7.3 Hyperammonemia with Concomitant Use of Valproate Concomitant administration of phenytoin and valproate… (Phenytoin label, Drug interactions)

…(cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels… (Phenytoin label, Drug interactions)

Concomitant medications were grouped as ACE inhibitors, oral anticoagulants, calcium channel blockers, beta blockers, cardiac glycosides, inducers of CYP3A4, substrates and inhibitors of CYP3A4, substrates and inhibitors of P-glycoprotein, nitrates, sulphonylureas, loop diuretics, potassium sparing diuretics, thiazide diuretics, substrates and inhibitors of tubular… (Dofetilide label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Effects on Vitamin D and Bone The chronic use of phenytoin in patients with epilepsy has been associated with decreased bone mineral density (osteopenia, osteoporosis, and osteomalacia) and bone fractures. (Phenytoin label, Warnings and precautions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Seizures and Seizure-like Activity : Weigh the potential risk versus benefits before prescribing dronabinol oral solution to patients with a history of seizures, including those requiring anti-epileptic medication or with other factors that lower the seizure threshold. (Dronabinol label, Warnings and precautions)

Following the administration of droperidol, the dose of other CNS depressant drugs should be reduced. (Droperidol label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric… (Phenytoin label, Drug interactions)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Other Agents Anticonvulsants: carbamazepine oxcarbazepine phenobarbital phenytoin ↓ TAF Consider alternative anticonvulsant. (Emtricitabine and tenofovir label, Drug interactions)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

If focal tremors, myoclonus, or seizures occur, patients should be evaluated neurologically, placed on anticonvulsant therapy if not already instituted, and the dosage of INVANZ re-examined to determine whether it should be decreased or discontinued. (Ertapenem label, Warnings and precautions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

Although behaviors such as sleep-driving may occur with sedative-hypnotics alone at therapeutic doses, the use of alcohol and other CNS depressants with sedative-hypnotics appears to increase the risk of such behaviors, as does the use of sedative-hypnotics at doses exceeding the maximum recommended dose. (Estazolam label, Warnings)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

Table 2: Drugs That Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine,… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

Strong CYP3A inducer and P-gp inducer : Increase the dosage as recommended. (Everolimus label, Drug interactions)

Strong CYP 3A4 inducers: Concomitant use of strong CYP 3A4 inducers decreases exemestane exposure. (Exemestane label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

…Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone,… (Phenytoin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

Phenobarbital Clinical Impact: Chronic administration of phenobarbital, a known enzyme inducer, may be associated with a decrease in the plasma half-life of fenoprofen. (Fenoprofen label, Drug interactions)

CYP3A4 Inducers No dosing adjustments are recommended in the presence of CYP3A4 inducers, such as rifampin and carbamazepine. (Fesoterodine label, Drug interactions)

Limited data in patients receiving known enzyme inducers ( phenytoin, phenobarbital, carbamazepine ) indicate only a 30% increase in the rate of flecainide elimination. (Flecainide label, Drug interactions)

…Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Possible risk factors for seizures include: concurrent major sedative-hypnotic drug withdrawal, recent therapy with repeated doses of parenteral benzodiazepines, myoclonic jerking or seizure activity prior to flumazenil administration in overdose cases, or concurrent cyclic antidepressant poisoning. (Flumazenil label, Warnings)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Reciprocal interactions may occur with concomitant use of fomepizole and drugs that increase or inhibit the cytochrome P450 system (e.g., phenytoin, carbamazepine, cimetidine, ketoconazole), though this has not been studied. (Fomepizole label, Drug interactions)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

• CYP3A4 Inducer: Increase IRESSA to 500 mg daily in patients receiving a strong CYP3A4 inducer. (Gefitinib label, Drug interactions)

…somatropin, protease inhibitors, atypical antipsychotic medications (e.g., olanzapine and clozapine), barbiturates, diazoxide, laxatives, rifampin, thiazides and other diuretics, corticosteroids, phenothiazines, thyroid hormones, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics (e.g., epinephrine, albuterol, terbutaline), and isoniazid. (Glimepiride label, Drug interactions)

…olanzapine and clozapine), corticosteroids, danazol, diuretics, estrogens, glucagon, isoniazid, niacin, oral contraceptives, phenothiazines, progestogens (e.g., in oral contraceptives), protease inhibitors, somatropin, sympathomimetic agents (e.g., albuterol, epinephrine, terbutaline), thyroid hormones, phenytoin, nicotinic acid, and calcium channel blocking drugs. (Glipizide label, Drug interactions)

Other Anticholinergic Drugs There is potential for an additive interaction between glycopyrrolate and concomitantly used anticholinergic drugs (e.g., tricyclic antidepressants, anti-epileptics, class I antiarrhythmics, anti­-spasmodics, amantadine) resulting in increased anticholinergic adverse reactions. (Glycopyrrolate label, Drug interactions)

…and its plasma concentrations can be significantly affected resulting in an increase in exposure Consider dose reduction [see Dosage and administration (2.7) ] Strong and moderate CYP3A4 inducers, e.g., rifampin, efavirenz Guanfacine is primarily metabolized by CYP3A4 and its plasma concentrations can be significantly affected resulting in a decrease in exposure… (Guanfacine label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Drugs that May Decrease Haloperidol Plasma Concentrations Coadministration of haloperidol with potent enzyme inducers of CYP3A4 may gradually decrease the plasma concentrations of haloperidol to such an extent that efficacy may be reduced. (Haloperidol label, Drug interactions)

…Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable. (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone,… (Phenytoin label, Drug interactions)

• CYP3A4 Inducers: Monitor for increased toxicity when used in combination with CYP3A4 inducers. (Ifosfamide label, Drug interactions)

CYP3A4 inducers may decrease Gleevec C max and area under curve (AUC). (Imatinib label, Drug interactions)

If focal tremors, myoclonus, or seizures occur, patients should be evaluated neurologically, placed on anticonvulsant therapy if not already instituted, and the dosage of PRIMAXIN re-examined to determine whether it should be decreased, or the antibacterial drug discontinued ( 5.2 ). (Imipenem and cilastatin label, Warnings and precautions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Concomitant Use with CYP3A Inducers Use of KALYDECO with strong CYP3A inducers, such as rifampin, substantially decreases the exposure of ivacaftor, which may reduce the therapeutic effectiveness of KALYDECO. (Ivacaftor label, Warnings and precautions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

Anticonvulsants: carbamazepine phenytoin phenobarbital ↓ ledipasvir ↓ sofosbuvir Coadministration of ledipasvir and sofosbuvir with carbamazepine, phenytoin, or phenobarbital is expected to decrease the concentration of ledipasvir and sofosbuvir, leading to reduced therapeutic effect of ledipasvir and sofosbuvir. (Ledipasvir and sofosbuvir label, Drug interactions)

Effects of VYKOURA on Other Drugs Certain Antiepileptic Drugs Increase monitoring for seizure activity in patients taking certain concomitant antiepileptic drugs. (Leucovorin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Effects of Leucovorin Products on Other Drugs Antiepileptic Drugs Folic acid in large amounts may counteract the antiepileptic effect of phenobarbital, phenytoin and primidone and increase the frequency of seizures in susceptible children. (Levoleucovorin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

Phenytoin and carbamazepine reduce serum protein binding of levothyroxine, and total and free T4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. (Levothyroxine label, Drug interactions)

Possible early warning signs of central nervous system (CNS) toxicity are restlessness, anxiety, incoherent speech, lightheadedness, metallic taste, tinnitus, dizziness, blurred vision, tremors, twitching, CNS depression, or drowsiness. (Lidocaine and epinephrine label, Warnings and precautions)

…prilocaine, procaine, ropivacaine, tetracaine Antineoplastic agents cyclophosphamide, flutamide, hydroxyurea, isofamide, rasburicase Antibiotics dapsone, nitrofurantoin, para-aminosalicylic acid, sufonamides Antimalarials chloroquine, primaquine Anticonvulsants Phenobarbital, phenytoin, sodium valproate Other drugs acetaminophen, metoclopramide, quinine, sulfasalazine (Lidocaine and prilocaine label, Drug interactions)

Strong P-glycoprotein/CYP3A4 inducer: The efficacy of TRADJENTA may be reduced when administered in combination (e.g., with rifampin). (Linagliptin label, Drug interactions)

Inducers of P-glycoprotein or CYP3A4 Enzymes Clinical Impact Rifampin decreased linagliptin exposure, suggesting that the efficacy of linagliptin may be reduced when administered in combination with a strong P-gp or CYP3A4 inducer. (Linagliptin and metformin label, Drug interactions)

Phenytoin and carbamazepine reduce serum protein binding of thyroid hormones, and total and FT4 may be reduced by 20% to 40%, but most patients have normal serum TSH levels and are clinically euthyroid. (Liothyronine label, Drug interactions)

Methyldopa, Phenytoin and Carbamazepine Clinical Impact: Concomitant use may increase risk of adverse reactions of these drugs. (Lithium label, Drug interactions)

Increased Risk of CNS Depression with Concomitant use of CNS Depressant Drugs : Lofexidine tablets potentiates the CNS depressant effects of benzodiazepines and may potentiate the CNS depressant effects of alcohol, barbiturates, and other sedating drugs. (Lofexidine label, Warnings and precautions)

• If patients with severe renal impairment or ESRD receiving SELZENTRY (without concomitant CYP3A inducers or inhibitors) experience postural hypotension, the dose of SELZENTRY should be reduced from 300 mg twice daily to 150 mg twice daily. (Maraviroc label, Warnings and precautions)

• Coadministration of meclizine hydrochloride with other CNS depressants, including alcohol, may result in increased CNS depression ( 7.1 ). (Meclizine label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Anticonvulsants In patients taking an anticonvulsant (e.g., valproic acid, carbamazepine, phenobarbital or phenytoin), the concomitant use of mefloquine may reduce seizure control by lowering the plasma levels of the anticonvulsant. (Mefloquine label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Inducers of CYP3A4 (e.g., phenytoin, carbamazepine, dexamethasone, rifampin, and phenobarbital) could increase the rate of elimination of donepezil. (Memantine and donepezil label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

…procaine, ropivacaine, tetracaine Antineoplastic agents cyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicase Antibiotics dapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamides Antimalarials chloroquine, primaquine Anticonvulsants phenobarbital, phenytoin, sodium valproate Other drugs acetaminophen, metoclopramide, quinine, sulfasalazine (Mepivacaine label, Drug interactions)

Additive Effects Since the effects of meprobamate and alcohol or meprobamate and other CNS depressants or psychotropic drugs may be additive,appropriate caution should be exercised with patients who take more than one of these agents simultaneously. (Meprobamate label, Warnings)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

Patients receiving ATMEKSI (methocarbamol) Oral Suspension should be cautioned about combined effects with alcohol and other CNS depressants [ see Drug Interactions (7.1) ]. (Methocarbamol label, Warnings and precautions)

Additionally, consider alternatives to structurally similar drugs such as carboxamides (e.g., carbamazepine), barbiturates, succinimides, and oxazolidinediones (e.g., trimethadione) in these same patients. (Phenytoin label, Warnings and precautions)

…2: Drugs That Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine,… (Phenytoin label, Drug interactions)

CYP3A4 inducers Drugs (e.g. nevirapine, rifampin) that are strong inducers of CYP3A4 are likely to decrease the pharmacological action of methylergonovine maleate. (Methylergonovine label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Inducers of CYP450 Liver Enzymes The simultaneous administration of LIKMEZ and drugs that induce microsomal liver enzymes, such as phenytoin or phenobarbital, may accelerate the elimination of metronidazole, resulting in reduced plasma concentrations of metronidazole. (Metronidazole label, Drug interactions)

Concurrent use of metyrosine with alcohol or other CNS depressants can increase their sedative effects. (Metyrosine label, Drug interactions)

…Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine 7.3 Hyperammonemia with Concomitant Use of Valproate Concomitant administration of phenytoin and valproate has been associated with an increased… (Phenytoin label, Drug interactions)

…Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine),… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Effects of PROVIGIL on CYP2C19 Substrates Elimination of drugs that are substrates for CYP2C19 (e.g., phenytoin, diazepam, propranolol, omeprazole, and clomipramine) may be prolonged by PROVIGIL via inhibition of metabolic enzymes, with resultant higher systemic exposure. (Modafinil label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

WARNINGS AND PRECAUTIONS Risk of Recurrent Respiratory and CNS Depression : Due to the duration of action of naloxone relative to the opioid, respiratory and CNS depression may recur after the first dose of naloxone. (Naloxone label, Warnings and precautions)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

Drugs and Herbals That May Reduce the Blood-Glucose-Lowering Effect of Nateglinide and Increase Susceptibility to Hyperglycemia Drugs: Thiazides, corticosteroids, thyroid products, sympathomimetics, somatropin, somatostatin analogues (e.g., lanreotide, octreotide), and CYP inducers (e.g., rifampin, phenytoin and St John's Wort). (Nateglinide label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Anticonvulsants: Carbamazepine, clonazepam, ethosuximide Plasma concentrations of nevirapine and the anticonvulsant may be decreased. (Nevirapine label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

Coadministration with oral doses of a P-gp and CYP3A4 inducer, rifampicin, decreased exposure to nintedanib by 50%. (Nintedanib label, Drug interactions)

Clinically Significant Interactions Affecting Co-Administered Drugs Sensitive CYP2C9 Substrates (e.g., celecoxib, tolbutamide) or CYP2C9 Substrates with a Narrow Therapeutic Index (e.g., phenytoin, warfarin) Clinical Impact Increased exposure of the co-administered drugs metabolized by CYP2C9. [see Clinical Pharmacology ( 12.3 )] Prevention or Management Reduce the… (Nitisinone label, Drug interactions)

…Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone,… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

Phenytoin, Carbamazepine, and Rifampin In patients treated with potent inducers of CYP3A4 (i.e., phenytoin, carbamazepine, and rifampin), the clearance of ondansetron was significantly increased and ondansetron blood concentrations were decreased. (Ondansetron label, Drug interactions)

Drug Interactions and Decreased Vitamin Absorption ORLISTAT may interact with concomitant drugs including cyclosporine, levothyroxine, warfarin, amiodarone, antiepileptic drugs, and antiretroviral drugs [see Drug Interactions (7) ]. (Orlistat label, Warnings and precautions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

Patients should be warned that the effects of alcohol or other CNS-depressant drugs may be additive to those of Oxazepam, possibly requiring adjustment of dosage or elimination of such agents. (Oxazepam label, Warnings)

Table 2: Drugs That Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine,… (Phenytoin label, Drug interactions)

Table 3: Drugs Affected by Phenytoin Interacting Agent Examples Drugs whose efficacy is impaired by phenytoin Azoles Fluconazole, ketoconazole, itraconazole, posaconazole, voriconazole Antineoplastic agents Irinotecan, paclitaxel, teniposide Delavirdine Phenytoin can substantially reduce the concentrations of delavirdine. (Phenytoin label, Drug interactions)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

Effects on Vitamin D and Bone The chronic use of phenytoin in patients with epilepsy has been associated with decreased bone mineral density (osteopenia, osteoporosis, and osteomalacia) and bone fractures. (Phenytoin label, Warnings and precautions)

…Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic… (Phenytoin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

If the patient is being treated with an anticonvulsant agent, increased dosage of that agent may be required when perphenazine products are used concomitantly. (Perphenazine label, Warnings)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

…Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline… (Phenytoin label, Drug interactions)

…somatropin, protease inhibitors, atypical antipsychotic medications (e.g., olanzapine and clozapine), barbiturates, diazoxide, laxatives, rifampin, thiazides and other diuretics, corticosteroids, phenothiazines, thyroid hormones, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics (e.g., epinephrine, albuterol, terbutaline), and isoniazid. (Pioglitazone and glimepiride label, Drug interactions)

Strong CYP3A4 Inducers: Decreased exposure of WAKIX; consider dosage adjustment of WAKIX ( 2.6 , 7.1 ) (Pitolisant label, Drug interactions)

Strong CYP3A4 and UGT1A1 Inducers In vitro assessments and limited clinical data indicated that concomitant use of strong CYP3A4 and UGT1A1 inducers (e.g., rifampin, phenytoin, carbamazepine) may decrease the systemic exposure of ponesimod. (Ponesimod label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

…cyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicase Antibiotics dapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamides Antimalarials chloroquine, primaquine Anticonvulsants phenobarbital, phenytoin, sodium valproate Other drugs acetaminophen, metoclopramide, quinine, sulfasalazine The administration of local anesthetic injections containing… (Prilocaine and epinephrine label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Therefore, use of procainamide should be considered only if discontinuation of digitalis, and therapy with potassium, lidocaine, or phenytoin are ineffective. (Procainamide label, Warnings)

However, it has been reported that phenothiazines may interfere with the metabolism of Dilantin ® ‡ and thus precipitate Dilantin toxicity. (Prochlorperazine label, Precautions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

The impairment may be amplified by concomitant use of other central-nervous-system depressants such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore such agents should either be eliminated or given in reduced dosage in the presence of promethazine… (Promethazine label, Warnings)

The impairment may be amplified by concomitant use of other central-nervous-system depressants such as alcohol, sedatives/hypnotics (including barbiturates), narcotics, narcotic analgesics, general anesthetics, tricyclic antidepressants, and tranquilizers; therefore such agents should either be eliminated or given in reduced dosage in the presence of promethazine… (Promethazine and dextromethorphan label, Warnings)

As with other sedative medications, there is wide interpatient variability in DIPRIVAN dosage requirements, and these requirements may change with time. (Propofol label, Warnings and precautions)

CYP1A2 and CYP2C19 Inducers: CYP1A2 inducers (e.g., phenytoin, montelukast, smoking) and CYP2C19 inducers (e.g. rifampin) decrease the plasma levels of propranolol resulting in a loss of efficacy [see Clinical Pharmacology ( 12.7 )] . (Propranolol label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine 7.3 Hyperammonemia with Concomitant Use of Valproate Concomitant administration of phenytoin and valproate has been associated with an increased risk of valproate-associated… (Phenytoin label, Drug interactions)

…decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs… (Phenytoin label, Drug interactions)

…topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake,… (Phenytoin label, Drug interactions)

The use of alcohol and other CNS depressants may increase the risk of such behaviors. (Ramelteon label, Warnings and precautions)

…Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone,… (Phenytoin label, Drug interactions)

CYP2C8 and CYP3A4 Inducers Intervention: Repaglinide tablets dose increases and increased frequency of glucose monitoring may be required when co‑administered. (Repaglinide label, Drug interactions)

Drug Interactions Effect of Rifabutin on the Pharmacokinetics of Other Drugs Rifabutin induces CYP3A enzymes and therefore may reduce the plasma concentrations of drugs metabolized by those enzymes. (Rifabutin label, Drug interactions)

…Disopyramide, mexiletine, quinidine, tocainide Antibiotics Chloramphenicol, clarithromycin, dapsone, doxycycline; Fluoroquinolones (such as ciprofloxacin) Oral Anticoagulants Warfarin Anticonvulsants Phenytoin Antimalarials Quinine Azole Antifungals Fluconazole, itraconazole, ketoconazole Antipsychotics Haloperidol Barbiturates Phenobarbital Benzodiazepines Diazepam… (Rifapentine label, Drug interactions)

Carbamazepine and other enzyme inducers decrease plasma concentrations of risperidone. (Risperidone label, Drug interactions)

Reduced Rocuronium Bromide Injection activity possible : Anticonvulsants. (Rocuronium label, Drug interactions)

…cyclophosphamide, flutamide, hydroxyurea, ifosfamide, rasburicase Antibiotics dapsone, nitrofurantoin, para-aminosalicylic acid, sulfonamides Antimalarials chloroquine, primaquine Anticonvulsants Phenobarbital, phenytoin, sodium valproate Other drugs acetaminophen, metoclopramide, quinine, sulfasalazine NAROPIN should be used with caution in patients receiving… (Ropivacaine label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Strong CYP3A4 Inducers Concomitant use of JAKAFI/JAKAFI XR with strong CYP3A4 inducers may decrease ruxolitinib exposure [ see Clinical Pharmacology ( 12.3 )] , which may reduce efficacy of JAKAFI/JAKAFI XR. (Ruxolitinib label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

Weigh this potential risk against the benefits before prescribing TRANSDERM SCŌP to patients with a history of seizures, including those receiving anti-epileptic medication or who have risk factors that can lower the seizure threshold. (Scopolamine label, Warnings and precautions)

Drugs that induce CYP3A4 (e.g., phenytoin, carbamazepine, nafcillin, phenobarbital, and rifampin) should be used with caution. (Selegiline label, Drug interactions)

…have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban Antiepileptic drugs The effect of phenytoin… (Phenytoin label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

…fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate,… (Phenytoin label, Drug interactions)

…Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines,… (Phenytoin label, Drug interactions)

…voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen,… (Phenytoin label, Drug interactions)

• CYP3A4 Inducers : Consider dose increase of SUTENT when administered with strong CYP3A4 inducers. (Sunitinib label, Drug interactions)

Co-administration with other CNS depressants (e.g., benzodiazepines, opioids, tricyclic antidepressants, alcohol) increases the risk of CNS depression. (Suvorexant label, Warnings and precautions)

Risk of Rejection with Strong CYP3A Inducers and Risk of Serious Adverse Reactions with Strong CYP3A Inhibitors The concomitant use of strong CYP3A inducers may increase the metabolism of tacrolimus, leading to lower whole blood trough concentrations and greater risk of rejection. (Tacrolimus label, Warnings and precautions)

CYP3A4 inhibitors (e.g. ketoconazole, ritonavir) increase CIALIS exposure ( 2.7 , 5.10 , 7.2 ) requiring dose adjustment: CIALIS for use as needed: no more than 10 mg every 72 hours CIALIS for once daily use: dose not to exceed 2.5 mg CYP3A4 inducers (e.g. rifampin) decrease CIALIS exposure ( 7.2 ). (Tadalafil label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

Although behaviors such as “sleep-driving” may occur with temazepam capsules alone at therapeutic doses, the use of alcohol and other CNS depressants with temazepam capsules appear to increase the risk of such behaviors, as does the use of temazepam capsules at doses exceeding the maximum recommended dose. (Temazepam label, Warnings)

Co-administration with Inducers or Inhibitors of CYP3A Metabolism Agents Inducing CYP3A Metabolism: Strong inducers of CYP3A4/5 such as dexamethasone, carbamazepine, phenytoin, phenobarbital, rifampin, rifabutin, and rifampacin may decrease exposure of the active metabolite, sirolimus. (Temsirolimus label, Warnings and precautions)

Terbinafine clearance is increased 100% by rifampin, a CYP450 enzyme inducer, and decreased 33% by cimetidine, a CYP450 enzyme inhibitor. (Terbinafine label, Drug interactions)

Alcohol or Other Sedating Drugs Concomitant use of alcohol or other sedating drugs may have additive effects and worsen sedation and somnolence [see Warnings and Precautions (5.7) ] . (Tetrabenazine label, Drug interactions)

John’s wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications. (Phenytoin label, Drug interactions)

DRUG INTERACTIONS Hepatic microsomal enzyme inducing agents, such as carbamazepine, were found to significantly increase the clearance of thiothixene. (Thiothixene label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

Phenytoin, Fosphenytoin: Concomitant administration of oral metronidazole and intravenous phenytoin was reported to result in prolongation of the half-life and reduction in the clearance of phenytoin. (Tinidazole label, Drug interactions)

Carbamazepine, felbamate, lamotrigine, topiramate, oxcarbazepine, lacosamide Antilipidemic agents Atorvastatin, fluvastatin, simvastatin Antiplatelets Ticagrelor Antiviral agents Efavirenz, lopinavir/ritonavir, indinavir, nelfinavir, ritonavir, saquinavir Fosamprenavir: phenytoin when given with fosamprenavir alone may decrease the concentration of amprenavir,… (Phenytoin label, Drug interactions)

Sedation: Zanaflex may interfere with everyday activities; sedative effects of Zanaflex, alcohol, and other central nervous system (CNS) depressants are additive ( 5.3 , 7.4 ) (Tizanidine label, Warnings and precautions)

…exposure to tofacitinib Intervention Dosage modification of XELJANZ/XELJANZ XR is recommended [see Dosage and Administration (2) , Clinical Pharmacology, Figure 3 (12.3) ] Strong CYP3A4 Inducers (e.g., rifampin) Clinical Impact Decreased exposure to tofacitinib and may result in loss of or reduced clinical response Intervention Concomitant use with XELJANZ/XELJANZ… (Tofacitinib label, Drug interactions)

…Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Co-administration of a CYP2C8 enzyme inducer (e.g., rifampin) may decrease exposure to treprostinil. (Treprostinil label, Warnings and precautions)

Warfarin Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin Other Corticosteroids, doxycycline, estrogens, furosemide, oral contraceptives, paroxetine, quinidine, rifampin, sertraline, theophylline, and vitamin D Drugs whose level is decreased by phenytoin Anticoagulants Apixaban, dabigatran, edoxaban, rivaroxaban… (Phenytoin label, Drug interactions)

However, it has been reported that phenothiazines may interfere with the metabolism of phenytoin and thus precipitate phenytoin toxicity. (Trifluoperazine label, Precautions)

Concurrent use of alcohol or other CNS depressants with trihexyphenidyl may cause increased sedative effects. (Trihexyphenidyl label, Drug interactions)

The recent use of other drugs that cause CNS depression or EPS symptoms may also increase the risk; consider reducing the dosage or discontinuing the drug. (Trimethobenzamide label, Warnings and precautions)

…Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine,… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine… (Phenytoin label, Drug interactions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

The interaction may result from reduced absorption of phenytoin and an increase in the rate of its metabolism and elimination. (Vincristine label, Drug interactions)

Effects on Vitamin D and Bone The chronic use of phenytoin in patients with epilepsy has been associated with decreased bone mineral density (osteopenia, osteoporosis, and osteomalacia) and bone fractures. (Phenytoin label, Warnings and precautions)

…Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine,… (Phenytoin label, Drug interactions)

…sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin. (Phenytoin label, Drug interactions)

Pharmacokinetic Interactions Carbamazepine Carbamazepine is an inducer of CYP3A4; administration of 200 mg twice daily for 21 days resulted in a decrease of approximately 35% in the AUC of ziprasidone. (Ziprasidone label, Drug interactions)

Limited evidence suggests that HLA-B*1502 may be a risk factor for the development of SJS/TEN in patients of Asian ancestry taking other antiepileptic drugs associated with SJS/TEN, including phenytoin. (Phenytoin label, Warnings and precautions)

These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel-blocking drugs, and isoniazid. (Acarbose label, Drug interactions)

Concomitant taking of P-gp inducers (including but not limited to rifampicin, carbamazepine, phenytoin, phenobarbital, and St. (Afatinib label, Drug interactions)

Examples rifampin, carbamazepine, phenytoin (Aprepitant label, Drug interactions)

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. (Phenytoin label, Drug interactions)

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. (Phenytoin label, Drug interactions)

In addition, the beneficial effects of levodopa in Parkinson’s disease have been reported to be reversed by phenytoin and papaverine. (Carbidopa label, Drug interactions)

Anticonvulsant therapy should be continued in patients with known seizure disorders. (Cefazolin label, Warnings and precautions)

Anticonvulsant therapy can be given if clinically indicated. (Cephalexin label, Warnings and precautions)

No depressant effect on blood levels in humans was noted when colestipol hydrochloride was administered with any of the following drugs: aspirin, clindamycin, clofibrate, methyldopa, nicotinic acid (niacin), tolbutamide, phenytoin or warfarin. (Colestipol label, Drug interactions)

These medications include thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. (Dapagliflozin and metformin label, Drug interactions)

Antihistamines Amphetamines may counteract the sedative effect of antihistamines. (Dextroamphetamine label, Drug interactions)

• Cytochrome P450 3A4 inducers, inhibitors, or substrates: May alter docetaxel metabolism. (Docetaxel label, Drug interactions)

Use alternative treatment that does not include carbamazepine where possible for INSTI-experienced patients with certain INSTI-associated resistance substitutions or clinically suspected INSTI resistance. b Oxcarbazepine Phenytoin Phenobarbital St. (Dolutegravir label, Drug interactions)

In Drug-Induced CNS and Respiratory Depression Doxapram alone may not stimulate adequate spontaneous breathing or provide sufficient arousal in patients who are severely depressed either due to respiratory failure or to CNS depressant drugs, but may be used as an adjunct to established supportive measures and resuscitative techniques. (Doxapram label, Warnings)

Concurrent use of alcohol and other CNS depressants (such as hypnotic sedatives and tranquilizers) with doxylamine succinate and pyridoxine hydrochloride delayed-release tablets is not recommended. (Doxylamine and pyridoxine label, Drug interactions)

These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. (Empagliflozin and metformin label, Drug interactions)

The “gasping syndrome” is characterized by central nervous system (CNS) depression, metabolic acidosis, and gasping respirations. (Epoetin alfa label, Warnings and precautions)

Effects of Other Drugs on HALAVEN No drug-drug interactions are expected with CYP3A4 inhibitors, CYP3A4 inducers or P-glycoprotein (P-gp) inhibitors. (Eribulin label, Drug interactions)

In addition, there have been reports of interactions of erythromycin with drugs not thought to be metabolized by CYP3A, including hexobarbital, phenytoin, and valproate. (Erythromycin label, Drug interactions)

Phenytoin Etodolac has no apparent pharmacokinetic interaction when administered with phenytoin. (Etodolac label, Drug interactions)

These drugs include thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. (Glipizide and metformin label, Precautions)

These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. (Glyburide label, Drug interactions)

Examples: Thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid. (Glyburide and metformin label, Drug interactions)

Potential for Glycerol Phenylbutyrate to Affect Other Drugs Drugs with narrow therapeutic index that are substrates of CYP3A4 Glycerol phenylbutyrate is a weak inducer of CYP3A4 in humans. (Glycerol phenylbutyrate label, Drug interactions)

• Furosemide, the benzodiazepines and phenytoin are incompatible with hyaluronidase ( 7.1 ) (Hyaluronidase label, Drug interactions)

Antiepileptics The activity of antiepileptic drugs might be impaired if co-administered with PLAQUENIL. (Hydroxychloroquine label, Drug interactions)

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. (Phenytoin label, Drug interactions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Antiepileptic Drugs Sporadic cases of seizures have been reported during concomitant use of ketorolac tromethamine and antiepileptic drugs (phenytoin, carbamazepine). (Ketorolac label, Drug interactions)

Therefore, ambulatory patients should be warned about activities requiring alertness (e.g., operating vehicles or machinery) and about concomitant use of alcohol and other CNS depressants. (Loxapine label, Warnings)

Examples: Thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid. (Metformin label, Drug interactions)

Anticonvulsants, psychotropic, hormone preparations, corticosteroids, antithyroid agents, cyproheptadine: may affect the results of the metyrapone test. (Metyrapone label, Drug interactions)

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. (Phenytoin label, Drug interactions)

These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid. (Pioglitazone and metformin label, Drug interactions)

…to date with the following: (1) cardiac glycosides– digitalis and digoxin; (2) hypoglycemics–insulin, chlorpropamide, phenformin, tolazamide, and tolbutamide; (3) tranquilizers and sedatives–chlordiazepoxide, diazepam, and phenobarbital; (4) antigout–allopurinol, colchicine, and probenecid; (5) antiarrhythmics–procainamide, propranolol (see WARNINGS however),… (Prazosin label, Drug interactions)

The impact of other inducers of drug metabolizing enzymes, such as phenytoin and phenobarbital, on UGT1A1 is unknown. (Raltegravir label, Drug interactions)

CYP3A4 Substrates An in vitro study has suggested that rifaximin induces CYP3A4 [see Clinical Pharmacology ( 12.3 )] . (Rifaximin label, Drug interactions)

Strong CYP3A inducers: Strong inducers of CYP3A (for example, rifampin, phenytoin, carbamazepine, phenobarbital or St. (Riociguat label, Drug interactions)

These medications include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. (Saxagliptin and metformin label, Drug interactions)

Examples: Thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blockers, and isoniazid. (Sitagliptin and metformin label, Drug interactions)

Sixteen (16) drugs tested did not show an in vitro interaction with LOKELMA (allopurinol, apixaban, aspirin, captopril, cyclosporine, digoxin, ethinyl estradiol, lisinopril, magnesium, metformin, phenytoin, prednisone, propranolol, quinapril, spironolactone and ticagrelor). (Sodium zirconium cyclosilicate label, Drug interactions)

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. (Phenytoin label, Drug interactions)

These data suggest that GH may alter the clearance of compounds known to be metabolized by CYP450 liver enzymes (e.g., corticosteroids, sex steroids, anticonvulsants, and cyclosporine). (Tesamorelin label, Drug interactions)

Hyperglycemia Hyperglycemia, resulting from the drug’s inhibitory effects on insulin release, has been reported. (Phenytoin label, Warnings and precautions)

Torsemide may affect the efficacy and safety of sensitive CYP2C9 substrates or of substrates with a narrow therapeutic range, such as warfarin or phenytoin. (Torsemide label, Drug interactions)

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. (Phenytoin label, Drug interactions)

No formal drug-drug interaction studies with zafirlukast and other drugs known to be metabolized by the cytochrome P450 2C9 isoenzyme (e.g., tolbutamide, phenytoin, carbamazepine) have been conducted; however, care should be exercised when zafirlukast is coadministered with these drugs . (Zafirlukast label, Precautions)

Drug-drug interaction studies in healthy subjects have been conducted with zileuton immediate-release tablets and digoxin, phenytoin, sulfasalazine, and naproxen. (Zileuton label, Drug interactions)

Drugs Having No Clinically Important Interactions with SAPHRIS No dosage adjustment of SAPHRIS is necessary when administered concomitantly with paroxetine (see Table 12 in Drug Interactions ( 7.1 ) for paroxetine dosage adjustment), imipramine, cimetidine, valproate, lithium, or a CYP3A4 inducer (e.g., carbamazepine, phenytoin, rifampin). (Asenapine label, Drug interactions)

In vitro data in human plasma indicate that Doxazosin has no effect on protein binding of digoxin, warfarin, phenytoin, or indomethacin. (Doxazosin label, Drug interactions)

CYP2C19 and CYP3A4 Inducer Co-administration of Micafungin in Sodium Chloride Injection with rifampin and ritonavir did not alter the pharmacokinetics of micafungin. (Micafungin label, Drug interactions)

…adjustment is needed when SINGULAIR is co-administered with theophylline, prednisone, prednisolone, oral contraceptives, fexofenadine, digoxin, warfarin, gemfibrozil, itraconazole, thyroid hormones, sedative hypnotics, non-steroidal anti-inflammatory agents, benzodiazepines, decongestants, and Cytochrome P450 (CYP) enzyme inducers [see Clinical Pharmacology (12.3) ]. (Montelukast label, Drug interactions)