Dextromethorphan and quinidine interactions

Interactions with Drugs Affecting Cytochrome P450 Isoenzymes The effects of concomitant use or discontinuation of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with codeine are complex. (Acetaminophen and codeine label, Boxed warning)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin Syndrome: Increased risk when co-administered with serotonergic agents (e.g., SSRIs, SNRIs, triptans), but also during overdosage situations. (Amphetamine label, Warnings and precautions)

Serotonin Syndrome: Increased risk when coadministered with serotonergic agents (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), triptans), but also during overdosage situations. (Amphetamine and dextroamphetamine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

The use of SAPHRIS should be avoided in combination with other drugs known to prolong QTc including Class 1A antiarrhythmics (e.g., quinidine, procainamide) or Class 3 antiarrhythmics (e.g., amiodarone, sotalol), antipsychotic medications (e.g., ziprasidone, chlorpromazine, thioridazine), and antibiotics (e.g., gatifloxacin, moxifloxacin). (Asenapine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

…bradyarrhythmias or uncompensated heart failure • patients on drugs known to prolong the QT interval • patients with ongoing proarrhythmic conditions such as uncorrected hypokalemia or hypomagnesemia, clinically significant bradycardia, and in patients receiving Class IA (quinidine, procainamide) or Class III (dofetilide, amiodarone, sotalol) antiarrhythmic agents. (Azithromycin label, Warnings and precautions)

• Serotonergic Drugs: Concomitant use may result in serotonin syndrome. (Belladonna and opium label, Drug interactions)

Serotonergic Drugs : Concomitant use may result in serotonin syndrome. (Buprenorphine label, Drug interactions)

Serotonergic Drugs: Concomitant use may result in serotonin syndrome. (Buprenorphine and naloxone label, Drug interactions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin Syndrome The development of a potentially life-threatening serotonin syndrome has been reported with SNRIs SSRIs, and other serotonergic drugs, including buspirone, alone but particularly with concomitant use of other serotonergic drugs (including triptans), with drugs that impair metabolism of serotonin (in particular, MAOIs, including reversible MAOIs… (Buspirone label, Warnings)

Examples: paroxetine, fluoxetine, bupropion, quinidine Benzodiazepines and Other Central Nervous System (CNS) Depressants Clinical Impact: Due to additive pharmacologic effect, the concomitant use of benzodiazepines or other CNS depressants, including alcohol, can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death. (Butalbital, acetaminophen, caffeine, and codeine label, Drug interactions)

Examples paroxetine, fluoxetine, bupropion, quinidine Benzodiazepines and other Central Nervous System (CNS) Depressants Clinical Impact: Due to additive pharmacologic effect, the concomitant use of benzodiazepines or other CNS depressants including alcohol, increases the risk of respiratory depression, profound sedation, coma, and death. (Butalbital, aspirin, caffeine, and codeine label, Drug interactions)

…medical attention if they ‎experience symptoms of hyperalgesia, including worsening pain, increased ‎sensitivity to pain, or new pain [see WARNINGS ; ADVERSE REACTIONS ].‎ Serotonin Syndrome Inform patients that butorphanol tartrate could cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs. (Butorphanol label, Precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

…syndrome, uncorrected electrolyte imbalance, such as hypokalemia or hypomagnesemia and cardiac disease, such as heart failure, myocardial infarction, or bradycardia), and patients receiving Class IA antiarrhythmic agents (quinidine, procainamide), or Class III antiarrhythmic agents (amiodarone, sotalol), tricyclic antidepressants, macrolides, and antipsychotics. (Ciprofloxacin label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Interactions with Drugs Affecting Cytochrome P450 Isoenzymes The effects of concomitant use or discontinuation of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with codeine are complex. (Codeine label, Boxed warning)

If serotonin syndrome symptoms occur with the use of other serotonergic drugs, immediately discontinue TONMYA. (Cyclobenzaprine label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

The dose of desipramine can then be adjusted based on clinical response; however, a dose above 40 mg/day is not recommended. (Dextromethorphan and quinidine label, Drug interactions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin Syndrome Serotonin syndrome, a potentially life-threatening reaction, may occur when amphetamines are used in combination with other drugs that affect the serotonergic neurotransmitter systems such as monoamine oxidase inhibitors (MAOIs), selective serotonin reuptake inhibitors (SSRIs), serotonin norepinephrine reuptake inhibitors (SNRIs), triptans,… (Dextroamphetamine label, Warnings)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Concomitant Antiarrhythmic Therapy The concomitant use of Norpace or Norpace CR with other Type 1A antiarrhythmic agents (such as quinidine or procainamide), Type 1C antiarrhythmics (such as encainide, flecainide or propafenone), and/or propranolol should be reserved for patients with life-threatening arrhythmias who are demonstrably unresponsive to single-agent… (Disopyramide label, Warnings)

Use with Drugs that Prolong QT Interval and Antiarrhythmic Agents The use of dofetilide in conjunction with other drugs that prolong the QT interval has not been studied and is not recommended. (Dofetilide label, Warnings)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Concomitant use of COMPLERA with drugs with a known risk to prolong the QTc interval of the electrocardiogram may increase the risk of Torsade de Pointes. (Emtricitabine, rilpivirine, and tenofovir label, Warnings and precautions)

…such as propranolol Cyclopropane or halogenated hydrocarbon anesthetics, such as halothane Antihistamines Thyroid hormones Diuretics Cardiac glycosides, such as digitalis glycosides Quinidine Drugs potentiating hypokalemic effects of epinephrine • Potassium depleting diuretics • Corticosteroids • Theophylline Epinephrine should not be used to counteract circulatory… (Epinephrine label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

• Serotonin Syndrome : Potentially life-threatening condition could result from concomitant serotonergic drug administration. (Fentanyl label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

(See DOSAGE and ADMINISTRATION. ) Because of the risk of QT prolongation and the potential for torsades de pointes, the use of FOSCAVIR should be avoided in combination with agents known to prolong the QT interval including Class IA (e.g., quinidine or procainamide) or Class III (e.g., dofetilide, amiodarone, sotalol) antiarrhythmic agents, phenothiazines, tricyclic… (Foscarnet label, Drug interactions)

Avoid co-administration of CONTEPO with drugs known to prolong the QT interval. (Fosfomycin label, Drug interactions)

Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of granisetron and other serotonergic drugs. (Granisetron label, Warnings and precautions)

Example: lactulose Serotonergic Drugs : Concomitant use may result in serotonin syndrome. (Hydrocodone label, Drug interactions)

Serotonin Syndrome Inform patients that hydrocodone bitartrate and acetaminophen tablets could cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs. (Hydrocodone and acetaminophen label, Precautions)

Serotonergic drugs : Concomitant use may result in serotonin syndrome. (Hydrocodone and chlorpheniramine label, Drug interactions)

Serotonergic Drugs : Concomitant use may result in serotonin syndrome. (Hydrocodone and homatropine label, Drug interactions)

S er otonin Syndrome Inform patients that opioids could cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs. (Hydrocodone and ibuprofen label, Precautions)

• Serotonergic Drugs : Concomitant use may result in serotonin syndrome. (Hydromorphone label, Drug interactions)

Therefore, PLAQUENIL is not recommended in patients taking other drugs that have the potential to prolong the QT interval. (Hydroxychloroquine label, Warnings and precautions)

Avoid the use of FANAPT in combination with any other drugs that prolong the QT interval [see Warnings and Precautions (5.3) ] . (Iloperidone label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Bradycardia may increase the risk of QT prolongation which may lead to severe ventricular arrhythmias, including torsade de pointes, especially in patients with risk factors such as use of QTc prolonging drugs [see Adverse Reactions ( 6.2 )] . (Ivabradine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Since it cannot be excluded that Lanreotide Injection may have this effect, avoid other drugs mainly metabolized by CYP3A4 and which have a low therapeutic index (e.g., quinidine, terfenadine). (Lanreotide label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Levofloxacin should be avoided in patients with known prolongation of the QT interval, patients with uncorrected hypokalemia, and patients receiving Class IA (quinidine, procainamide), or Class III (amiodarone, sotalol) antiarrhythmic agents. (Levofloxacin label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin Syndrome Inform patients that opioids could cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs. (Levorphanol label, Precautions)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

Serotonin Syndrome: Increased risk when co-administered with serotonergic agents (e.g., SSRIs, SNRIs, triptans), but also during overdosage situations. (Lisdexamfetamine label, Warnings and precautions)

If concomitant use of lithium with other serotonergic drugs is clinically warranted, inform patients of the increased risk for serotonin syndrome and monitor for symptoms. (Lithium label, Warnings and precautions)

Avoid loperamide hydrochloride capsules in: • combination with others drugs or herbal products that are known to prolong the QT interval, including Class 1A (e.g., quinidine, procainamide) or Class III (e.g., amiodarone, sotalol) antiarrhythmics, antipsychotics (e.g., chlorpromazine, haloperidol, thioridazine, ziprasidone), antibiotics (e.g., moxifloxacin), or… (Loperamide label, Warnings)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Concomitant use with quinidine, quinine, or mefloquine. (Dextromethorphan and quinidine label, Contraindications)

Serotonin syndrome has resulted from concomitant use of metaxalone (within the recommended dosage range) and other serotonergic drugs [see Warnings and Precautions (5.1) ]. (Metaxalone label, Drug interactions)

Interactions with Drugs Affecting Cytochrome P450 Isoenzymes The concomitant use of METHADOSE with all cytochrome P450 3A4, 2B6, 2C19, 2C9 or 2D6 inhibitors may result in an increase in methadone plasma concentrations, which could cause potentially fatal respiratory depression. (Methadone label, Boxed warning)

Serotonin Syndrome: Increased risk when coadministered with serotonergic agents (e.g., SSRIs, SNRIs, triptans), but also during overdosage situations. (Methamphetamine label, Warnings and precautions)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

CYP2D6 Inhibitors Monitor patients closely when the combination use of CYP2D6 inhibitor and metoprolol cannot be avoided. (Metoprolol label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

• Serotonin Syndrome : Increased risk when co-administered with other serotonergic agents, but also when taken alone. (Milnacipran label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

• Serotonergic Drugs: Concomitant use may result in serotonin syndrome. (Morphine label, Drug interactions)

The drug should be avoided in patients with known prolongation of the QT interval, patients with uncorrected hypokalemia and patients receiving Class IA (for example, quinidine, procainamide) or Class III (for example, amiodarone, sotalol) antiarrhythmic agents, due to the lack of clinical experience with the drug in these patient populations. (Moxifloxacin label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Ofloxacin should be avoided in patients with known prolongation of the QT interval, patients with uncorrected hypokalemia, and patients receiving Class IA (quinidine, procainamide), or Class III (amiodarone, sotalol) antiarrhythmic agents. (Ofloxacin label, Precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonergic Drugs : Concomitant use may result in serotonin syndrome. (Oliceridine label, Drug interactions)

Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of Ondansetron Injection and other serotonergic drugs. (Ondansetron label, Warnings and precautions)

Avoid coadministration of oxaliplatin injection with medicinal products with a known potential to prolong the QT interval. (Oxaliplatin label, Drug interactions)

Serotonergic Drug s: Concomitant use may result in serotonin syndrome. (Oxycodone label, Drug interactions)

Serotonergic Drugs : Concomitant use may result in serotonin syndrome. (Oxymorphone label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of POSFREA and other serotonergic drugs. (Palonosetron label, Warnings and precautions)

The dose of paroxetine can then be adjusted based on clinical response; however, dosage above 35 mg/day is not recommended. (Dextromethorphan and quinidine label, Drug interactions)

Avoid coadministration of VOTRIENT with drugs known to prolong the QT/QTc interval. (Pazopanib label, Drug interactions)

Serotonin Syndrome Inform patients that opioids could cause a rare but potentially life-threatening condition resulting from concomitant administration of serotonergic drugs. (Pentazocine and naloxone label, Precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

Drugs that Prolong the QT Interval : Avoid concomitant use. (Phenobarbital label, Drug interactions)

…use of NUPLAZID should be avoided in patients with known QT prolongation or in combination with other drugs known to prolong QT interval including Class 1A antiarrhythmics (e.g., quinidine, procainamide) or Class 3 antiarrhythmics (e.g., amiodarone, sotalol), certain antipsychotic medications (e.g., ziprasidone, chlorpromazine, thioridazine), and certain antibiotics… (Pimavanserin label, Warnings and precautions)

Concomitant use with drugs that both prolong QT interval and are metabolized by CYP2D6 (e.g., thioridazine or pimozide). (Dextromethorphan and quinidine label, Contraindications)

The use of WAKIX should be avoided in patients with known QT prolongation or in combination with other drugs known to prolong the QT interval [see Drug Interactions ( 7.1 )]. (Pitolisant label, Warnings and precautions)

Class Ia (e.g., quinidine, procainamide) and Class III (e.g., amiodarone, sotalol) anti-arrhythmic drugs have been associated with cases of Torsades de Pointes in patients with bradycardia. (Ponesimod label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Interactions with Drugs Affecting Cytochrome P450 Isoenzymes The effects of concomitant use or discontinuation of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with codeine are complex, requiring careful consideration of the effects on the parent drug, codeine, and the active metabolite, morphine. (Promethazine and codeine label, Boxed warning)

Avoid the use of propafenone with Class IA and III antiarrhythmic agents (including quinidine and amiodarone). (Propafenone label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Thrombocytopenia and Other Hypersensitivity Reactions Quinidine can cause immune-mediated thrombocytopenia that can be severe or fatal. (Dextromethorphan and quinidine label, Warnings and precautions)

Concomitant use with quinidine, quinine, or mefloquine. (Dextromethorphan and quinidine label, Contraindications)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

• Serotonin Syndrome : Potentially life-threatening condition could result from concomitant serotonergic drug administration. (Remifentanil label, Warnings and precautions)

…exposure Progestins Anticonvulsants Phenytoin Administered with rifampin 450 mg daily Decrease exposure Antiarrhythmics Disopyramide Decrease exposure Mexiletine Decrease exposure Quinidine Decrease exposure Propafenone Decrease AUC by 50%-67% Tocainide Decrease exposure Antiestrogens Tamoxifen Decrease AUC by 86% Toremifene Decrease steady state concentrations… (Rifampin label, Drug interactions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Class Ia antiarrhythmic drugs, such as disopyramide, quinidine, and procainamide, and other Class III drugs (for example, amiodarone) are not recommended as concomitant therapy, because of their potential for additive QTc prolongation [see Warnings and Precautions ( 5.1 )]. (Sotalol label, Drug interactions)

Combining St. John's wort with antidepressants and other serotonergic drugs increases the risk of serotonin syndrome. (NCCIH, St. John's Wort)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Certain conditions may increase the risk for torsade de pointes or sudden death such as (1) bradycardia; (2) hypokalemia or hypomagnesemia; (3) concomitant use of other drugs that prolong the QTc interval; and (4) presence of congenital prolongation of the QT interval [see Warnings and Precautions ( 5.8 ), Clinical Pharmacology (12.2) ]. (Tetrabenazine label, Drug interactions)

Concomitant use with drugs that both prolong QT interval and are metabolized by CYP2D6 (e.g., thioridazine or pimozide). (Dextromethorphan and quinidine label, Contraindications)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

The effects of concomitant use or discontinuation of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with tramadol are complex. (Tramadol label, Boxed warning)

Interactions with Drugs Affecting Cytochrome P450 Isoenzymes The effects of concomitant use or discontinuation of cytochrome P450 3A4 inducers, 3A4 inhibitors, or 2D6 inhibitors with tramadol are complex. (Tramadol and acetaminophen label, Boxed warning)

Use with an MAOI or within 14 days of stopping an MAOI. (Dextromethorphan and quinidine label, Contraindications)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Patients taking Class 1A (for example. quinidine, procainamide) or Class III (for example, amiodarone, sotalol) antiarrhythmic medications or those with congenital QT prolongation, should avoid using vardenafil hydrochloride tablets. (Vardenafil label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Avoid concomitant use of VEPPANU with strong CYP3A inhibitors or drugs known to prolong the QTc interval. (Vepdegestrant label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Prolongation: Monitor ECG if concomitant use of drugs that prolong QT interval cannot be avoided or if concomitant CYP3A4 inhibitors used. (Dextromethorphan and quinidine label, Warnings and precautions)

Serotonin syndrome: Use of NUEDEXTA with selective serotonin reuptake inhibitor (SSRIs) or tricyclic antidepressants increases the risk. (Dextromethorphan and quinidine label, Warnings and precautions)

Therefore, ziprasidone should not be given with: • dofetilide, sotalol, quinidine, other Class Ia and III anti-arrhythmics, mesoridazine, thioridazine, chlorpromazine, droperidol, pimozide, sparfloxacin, gatifloxacin, moxifloxacin, halofantrine, mefloquine, pentamidine, arsenic trioxide, levomethadyl acetate, dolasetron mesylate, probucol or tacrolimus. (Ziprasidone label, Contraindications)

Acetazolamide reduces urinary excretion of quinidine and may enhance its effect. (Acetazolamide label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Effect of P-glycoprotein (P-gp) Inhibitors and Inducers Concomitant taking of P-gp inhibitors (including but not limited to ritonavir, cyclosporine A, ketoconazole, itraconazole, erythromycin, verapamil, quinidine, tacrolimus, nelfinavir, saquinavir, and amiodarone) with GILOTRIF can increase exposure to afatinib [see Clinical Pharmacology (12.3) ]. (Afatinib label, Drug interactions)

Alcohol As with any other CNS drug, caution should be used when NUEDEXTA is taken in combination with other centrally acting drugs and alcohol. (Dextromethorphan and quinidine label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

MAO inhibitors, tricyclic antidepressants and drugs that prolong the QTc interval may potentiate effect on the cardiovascular system. (Arformoterol label, Drug interactions)

CYP2D6 inhibitors and CYP3A4 Inhibitors : See full prescribing information for ABILIFY MAINTENA dosage modifications when used concomitantly with CYP2D6 inhibitors and/or CYP3A4 inhibitors for greater than 14 days ( 7.1 ) (Aripiprazole label, Drug interactions)

Strong CYP2D6 Inhibitors Prevention or Management With concomitant use of atomoxetine oral solution and a strong CYP2D6 inhibitor 1 , increase the titration interval [see Dosage and Administration (2.5) and Clinical Pharmacology (12.3) ] . (Atomoxetine label, Drug interactions)

Drug Interactions Drugs which may enhance the neuromuscular blocking action of atracurium include: enflurane; isoflurane; halothane; certain antibiotics, especially the aminoglycosides and polymyxins; lithium; magnesium salts; procainamide; and quinidine. (Atracurium label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Drugs that Prolong the QT interval QT prolongation has been reported with metronidazole, a component of bismuth subcitrate potassium, metronidazole and tetracycline hydrochloride, particularly when administered with drugs with the potential for prolonging the QT interval. (Bismuth subcitrate, metronidazole, and tetracycline label, Warnings and precautions)

Strong CYP2D6 REXULTI may be administered without dosage adjustment in patients with MDD when administered with strong CYP2D6 inhibitors (e.g., paroxetine, fluoxetine). or CYP3A4 inhibitors Administer half of recommended dosage. (Brexpiprazole label, Drug interactions)

CYP2D6 inhibitors may potentiate systemic beta-blockade. (Brimonidine and timolol label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

CYP2D6 Inhibitors and Poor Metabolizers Interactions of carvedilol with potent inhibitors of CYP2D6 isoenzyme (such as quinidine, fluoxetine, paroxetine, and propafenone) have not been studied, but these drugs would be expected to increase blood levels of the R(+) enantiomer of carvedilol [see Clinical Pharmacology (12.3) ]. (Carvedilol label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

QT Interval Prolongation and V entricular A rr h ythmia Decreases in serum calcium can also prolong the QT interval, potentially resulting in ventricular arrhythmia. (Cinacalcet label, Warnings and precautions)

Potentiation of Neuromuscular Blockade Certain drugs may enhance the neuromuscular blocking action of Cisatracurium Besylate Injection including inhalational anesthetics, antibiotics, magnesium salts, lithium, local anesthetics, procainamide and quinidine [see Drug Interactions ( 7.1 )] . (Cisatracurium label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

The use of the P-gp inhibitors verapamil, amiodarone, quinidine, clarithromycin, and ticagrelor does not require a dosage adjustment of PRADAXA. (Dabigatran label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

…ergotamine, everolimus, felodipine, fentanyl, hormonal contraceptive agents, indinavir, fluticasone, lopinavir, lovastatin, lurasidone, maraviroc, midazolam, nisoldipine, pimozide, quetiapine, quinidine, saquinavir, sildenafil, simvastatin, sirolimus, tacrolimus, tolvaptan, tipranavir, triazolam, ticagrelor, and vardenafil) [see Clinical Pharmacology (12.3)] . (Deferasirox label, Drug interactions)

Carefully monitor cardiac rhythm when administering SUPRANE to susceptible patients (e.g., patients with congenital Long QT Syndrome or patients taking drugs that can prolong the QT interval). (Desflurane label, Warnings and precautions)

Concomitant use of strong CYP2D6 inhibitors: Maximum recommended dose of AUSTEDO XR or AUSTEDO is 36 mg per day ( 2.3 , 7.1 ) (Deutetrabenazine label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Digoxin: Increased digoxin substrate plasma concentration may occur. (Dextromethorphan and quinidine label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

CYP2D6 inhibitors may potentiate systemic beta-blockade. (Dorzolamide and timolol label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

…cardiac disease, 3) treatment with Class I and Class III antiarrhythmics, 4) treatment with monoamine oxidase inhibitors (MAOI's), 5) concomitant treatment with other drug products known to prolong the QT interval (see PRECAUTIONS, Drug Interactions ), and 6) electrolyte imbalance, in particular hypokalemia and hypomagnesemia, or concomitant treatment with drugs… (Droperidol label, Warnings)

Use caution in combination with moderate CYP3A4 inhibitors (e.g., erythromycin) or strong (e.g., paroxetine) or moderate CYP2D6 inhibitors, a combination of both CYP3A4 and CYP2D6 inhibitors, or known poor metabolizers of CYP2D6. (Dutasteride and tamsulosin label, Warnings and precautions)

QT Prolongation: Monitor for prolonged QT intervals in patients with congestive heart failure, bradyarrhythmias, drugs known to prolong the QT interval, and electrolyte abnormalities. (Eribulin label, Warnings and precautions)

The serum digoxin concentrations should be monitored and used for titration of the digoxin dose to obtain the desired clinical effect. amiodarone bepridil disopyramide flecainide lidocaine (systemic) mexiletine propafenone quinidine ↓ antiarrhythmics Concentrations of these antiarrhythmics may be decreased when co-administered with Etravirine. (Etravirine label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

(See DOSAGE AND ADMINISTRATION ) Drugs that inhibit cytochrome P450IID6, such as quinidine , might increase the plasma concentrations of flecainide in patients that are on chronic flecainide therapy; especially if these patients are extensive metabolizers. (Flecainide label, Drug interactions)

…Antidepressants, QTc Prolonging Drugs Formoterol, as with other beta 2 -agonists, should be administered with extreme caution to patients being treated with monoamine oxidase inhibitors, tricyclic antidepressants, or drugs known to prolong the QTc interval because the effect of adrenergic agonists on the cardiovascular system may be potentiated by these agents. (Formoterol label, Drug interactions)

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 on phenobarbital, valproic acid and sodium valproate serum levels… (Fosphenytoin label, Drug interactions)

CYP3A4 Substrates with narrow therapeutic index (e.g., alfentanil, quinidine, cyclosporine) : Glycerol phenylbutyrate may decrease exposure; monitor for decreased efficacy of the narrow therapeutic index drug ( 7.3 ) (Glycerol phenylbutyrate label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Effect on QT/QTc Interval: Androgen deprivation therapy may prolong the QT interval. (Goserelin label, Warnings and precautions)

The haloperidol plasma concentrations increased when a CYP3A4 and/or CYP2D6 inhibitor was coadministered with haloperidol. (Haloperidol label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Monitor QT interval when administering FORANE to susceptible patients (e.g., patients with congenital Long QT Syndrome or patients taking drugs that can prolong the QT interval). (Isoflurane label, Warnings and precautions)

TYKERB may prolong the QT interval in some patients. (Lapatinib label, Warnings and precautions)

Effect on QT/QTc Interval: Androgen deprivation therapy may prolong the QT interval. (Leuprolide label, Warnings and precautions)

Risk of QT Prolongation : Lofexidine tablets prolong the QT interval. (Lofexidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Use with Other N-methyl-D-aspartate (NMDA) Antagonists The combined use of memantine hydrochloride with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution. (Memantine label, Drug interactions)

Use of Memantine with Other N-methyl-D-aspartate (NMDA) Antagonists The combined use of memantine hydrochloride with other NMDA antagonists (amantadine, ketamine, and dextromethorphan) has not been systematically evaluated and such use should be approached with caution. (Memantine and donepezil label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Examples quinidine, bupropion, fluoxetine, and paroxetine Monoamine Oxidase Inhibitors Clinical Impact Increased risk of hypertension [see Warnings and Precautions ( 5.5 )] . (Metoclopramide label, Drug interactions)

CYP2D6 inhibitors: Increased metoprolol concentration. (Metoprolol and hydrochlorothiazide label, Drug interactions)

Drugs that Prolong the QT Interval QT prolongation has been reported, particularly when metronidazole was administered with drugs with the potential for prolonging the QT interval. (Metronidazole label, Drug interactions)

Serotonergic Drugs The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system, such as selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants (TCAs), triptans, 5-HT3 receptor antagonists, drugs that effect the serotonin neurotransmitter system… (Nalbuphine label, Drug interactions)

P-glycoprotein (P-gp) Inhibitors (e.g., amiodarone, captopril, cyclosporine, quercetin, quinidine, verapamil) Clinical Impact Increase in plasma naldemedine concentrations [see Clinical Pharmacology (12.3) ] Intervention Monitor for potential naldemedine-related adverse reactions [see Adverse Reactions (6.1) ] . (Naldemedine label, Drug interactions)

•Weak CYP3A4 inhibitors (e.g., quinidine, cimetidine) •Clinically significant increases in naloxegol concentrations are not expected. (Naloxegol label, Drug interactions)

Use with CYP2D6 Inhibitors Nebivolol exposure increases with inhibition of CYP2D6 [see Drug Interactions ( 7 ) ] . (Nebivolol label, Warnings and precautions)

Co-administration of multiple doses of quinidine sulfate, 200 mg t.i.d., and nifedipine, 20 mg t.i.d., increased C max and AUC of nifedipine in healthy volunteers by factors of 2.30 and 1.37, respectively. (Nifedipine label, Drug interactions)

Quinidine at 648 mg bid decreased the bioavailability (AUC) of nisoldipine by 26%, but not the peak concentration. (Nisoldipine label, Drug interactions)

Drugs Metabolized by CYP 450 Enzymes: concomitant use with other drugs mainly metabolized by CYP3A4 that have a narrow therapeutic index (e.g., quinidine) should be used with caution and increased monitoring may be required (‎ 7 ). (Octreotide label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

…combination with other drugs that are known to prolong QTc including Class 1A (e.g., quinidine, procainamide) or Class III (e.g., amiodarone, sotalol) antiarrhythmic medications, antipsychotic medications (e.g., chlorpromazine, thioridazine), antibiotics (e.g., gatifloxacin, moxifloxacin), or any other class of medications known to prolong the QTc interval. (Paliperidone label, Warnings and precautions)

Drugs that Prolong QT: Use with caution in patients who are at significant risk of developing QTc prolongation. (Pasireotide label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

…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)

QT Interval Prolonging Drugs The pharmacodynamic interaction potential to prolong the QT interval of the electrocardiogram between Primaquine phosphate Tablets and other drugs that effect cardiac conduction is unknown. (Primaquine label, Drug interactions)

Concurrent Other Antiarrhythmic Agents Concurrent use of PA with other Group 1A antiarrhythmic agents such as quinidine or disopyramide may produce enhanced prolongation of conduction or depression of contractility and hypotension, especially in patients with cardiac decompensation. (Procainamide label, Warnings)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Impact of Other Drugs on Propranolol CYP2D6, CYP1A2 and CYP2C19 Inhibitors: CYP2D6 inhibitors (e.g. bupropion, fluoxetine, paroxetine, quinidine), CYP1A2 inhibitors (e.g., ciprofloxacin, enoxamine, fluvoxamine) and CYP2C19 inhibitors (e.g., fluconazole, fluvoxamine, ticlopidine) increase exposure to propranolol when co-administered with INNOPRAN XL. (Propranolol label, Drug interactions)

…Class 1A antiarrythmics (e.g., quinidine, procainamide) or Class III antiarrythmics (e.g., amiodarone, sotalol), antipsychotic medications (e.g., ziprasidone, chlorpromazine, thioridazine), antibiotics (e.g., gatifloxacin, moxifloxacin), or any other class of medications known to prolong the QTc interval (e.g., pentamidine, levomethadyl acetate, methadone). (Quetiapine label, Warnings and precautions)

Table 4: Drug Interactions with PRIFTIN: Dosage Adjustment May be Necessary Drug Class Examples of Drugs Within Class Antiarrhythmics Disopyramide, mexiletine, quinidine, tocainide Antibiotics Chloramphenicol, clarithromycin, dapsone, doxycycline; Fluoroquinolones (such as ciprofloxacin) Oral Anticoagulants Warfarin Anticonvulsants Phenytoin Antimalarials Quinine… (Rifapentine label, Drug interactions)

In healthy subjects, 75 mg once daily and 300 mg once daily (3 times and 12 times the dose in EDURANT) have been shown to prolong the QTc interval of the electrocardiogram. (Rilpivirine label, Warnings and precautions)

P-gp Inhibitors Concomitant administration of NURTEC ODT with potent inhibitors of P-gp (e.g., amiodarone, cyclosporine, lapatinib, quinidine, ranolazine) may result in increased exposure of rimegepant. (Rimegepant label, Drug interactions)

Fluoxetine and Paroxetine Fluoxetine (20 mg once daily) and paroxetine (20 mg once daily), CYP 2D6 inhibitors, have been shown to increase the plasma concentration of risperidone 2.5–2.8 fold and 3–9 fold respectively. (Risperidone label, Drug interactions)

Certain inhalation anesthetics, particularly enflurane and isoflurane, antibiotics, magnesium salts, lithium, local anesthetics, procainamide, and quinidine have been shown to increase the duration of neuromuscular block and decrease infusion requirements of neuromuscular blocking agents [see Drug Interactions ( 7.3 )] . (Rocuronium label, Warnings and precautions)

Exposure to dextromethorphan, a CYP2D6 substrate, following a single dose of rolapitant increased about 3-fold on Days 8 and Day 22. (Rolapitant label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Caution should be exercised when administering sevoflurane to susceptible patients (e.g., patients with congenital Long QT Syndrome or patients taking drugs that can prolong the QT interval). (Sevoflurane label, Warnings)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Monitor electrolytes and electrocardiograms in patients with congestive heart failure, bradyarrhythmias, drugs known to prolong the QT interval, including Class Ia and III antiarrhythmics. (Sorafenib label, Warnings and precautions)

Drugs that May Enhance the Neuromuscular Blocking Action of Succinylcholine : promazine, oxytocin, aprotinin, certain non-penicillin antibiotics, quinidine, β-adrenergic blockers, procainamide, lidocaine, trimethaphan, lithium carbonate, magnesium salts, quinine, chloroquine, isoflurane, desflurane, metoclopramide, terbutaline, and drugs that reduce plasma cholinesterase… (Succinylcholine label, Drug interactions)

Drug Interactions Some studies have shown that simultaneous sucralfate administration in healthy volunteers reduced the extent of absorption (bioavailability) of single doses of the following: cimetidine, digoxin, fluoroquinolone antibiotics, ketoconazole, l-thyroxine, phenytoin, quinidine, ranitidine, tetracycline, and theophylline. (Sucralfate label, Drug interactions)

Drugs that Prolong QT Interval SUTENT is associated with QTc interval prolongation [see Warnings and Precautions (5.3) , Clinical Pharmacology (12.2) ] . (Sunitinib label, Drug interactions)

Use with caution in combination with moderate inhibitors of CYP3A4, with strong or moderate inhibitors of CYP2D6, in patients known to be CYP2D6 poor metabolizers, or in combination with other cytochrome P450 inhibitors. (Tamsulosin label, Warnings and precautions)

In studies in healthy subjects characterized as extensive metabolizers of dextromethorphan (antitussive drug and CYP2D6 probe substrate), terbinafine increases the dextromethorphan/ dextrorphan metabolite ratio in urine by 16- to 97-fold on average. (Terbinafine label, Drug interactions)

Potentiated systemic beta-blockade (e.g., decreased heart rate) has been reported during combined treatment with quinidine and timolol. (Timolol label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Agents generally accepted to prolong QT interval include Class 1A (e.g., quinidine, procainamide, disopyramide) and Class III (e.g., amiodarone, sotalol, ibutilide, dofetilide) antiarrhythmics; certain antipsychotics (e.g., thioridazine, haloperidol); certain antidepressants (e.g., venlafaxine, amitriptyline); certain antibiotics (e.g., erythromycin, clarithromycin,… (Toremifene label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Effect on QT/QTc Interval: Androgen deprivation therapy may prolong the QT interval. (Triptorelin label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Use of BCRP and/or P-gp only inhibitors (e.g., quinidine, carvedilol, eltrombopag, curcumin) may increase the exposure of ubrogepant [ s ee Clinical Pharmacology ( 12.3 ) ] . (Ubrogepant label, Drug interactions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

Anticholinergic effects of quinidine: Monitor for worsening in myasthenia gravis and other sensitive conditions. (Dextromethorphan and quinidine label, Warnings and precautions)

For patients who are CYP2D6 poor metabolizers or are taking a strong CYP2D6 inhibitor, dose reduction may be necessary. (Valbenazine label, Warnings and precautions)

CYP2D6 Substrates Clinical Impact Viloxazine is a weak inhibitor of CYP2D6, and increases the exposure of CYP2D6 substrates when coadministered [see Clinical Pharmacology (12.3) ] . (Viloxazine label, Drug interactions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

CYP2D6 substrates Clinical Impact: In vitro studies indicate that celecoxib, although not a substrate, is an inhibitor of CYP2D6. (Celecoxib label, Drug interactions)

Drugs which inhibit CYP2D6 and CYP3A3/4 also inhibit the metabolism of cevimeline. (Cevimeline label, Drug interactions)

The selective serotonin reuptake inhibitors sertraline (weak CYP3A4 inducer) and fluoxetine (CYP2D6 inhibitor), and the anti-epileptic drug felbamate (CYP2C19 inhibitor and CYP3A4 inducer) do not affect the pharmacokinetics of clonazepam. (Clonazepam label, Drug interactions)

Examples: α-adrenergic antagonists, β-adrenergic receptor antagonists, reserpine, quinidine, mephentermine Other Drug Interactions G u anethidine C linical Impact: Ephedrine may inhibit the neuron blockage produced by guanethidine, resulting in loss of antihypertensive effectiveness. (Ephedrine label, Drug interactions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

Strong and moderate CYP3A inhibitors include, but are not limited to, atazanavir, clarithromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin, amprenavir, aprepitant, diltiazem, erythromycin, fluconazole, fosamprenavir, grapefruit juice, and verapamil. (Dextromethorphan and quinidine label, Warnings and precautions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

A variety of antiarrhythmics such as quinidine or propranolol were also added, sometimes with improved control of ventricular ectopy. (Mexiletine label, Drug interactions)

…for Drug Interaction: It appears possible, although there is no supporting experimental evidence, that the high renal clearance of desglymidodrine (a base) is due to active tubular secretion by the base-secreting system also responsible for the secretion of such drugs as metformin, cimetidine, ranitidine, procainamide, triamterene, flecainide, and quinidine. (Midodrine label, Precautions)

…untoward clinical manifestations have been observed in limited experience with patients in whom milrinone was used concurrently with the following drugs: digitalis glycosides; lidocaine, quinidine; hydralazine, prazosin; isosorbide dinitrate, nitroglycerin; chlorthalidone, furosemide, hydrochlorothiazide, spironolactone; captopril; heparin, warfarin, diazepam, insulin;… (Milrinone label, Drug interactions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

In Vitro Interaction The plasma protein binding of nicardipine was not altered when therapeutic concentrations of furosemide, propranolol, dipyridamole, warfarin, quinidine, or naproxen were added to human plasma in vitro. (Nicardipine label, Drug interactions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

Serotonergic Drugs Clinical Impact: The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome [see Adverse Reaction ( 6.2)]. (Oxycodone and acetaminophen label, Drug interactions)

The safety and efficacy of combination therapy with phentermine and any other drug products for weight loss including prescribed drugs, over-the-counter preparations, and herbal products, or serotonergic agents such as selective serotonin reuptake inhibitors (e.g., fluoxetine, sertraline, fluvoxamine, paroxetine), have not been established. (Phentermine label, Warnings and precautions)

…tolazamide, and tolbutamide; (3) tranquilizers and sedatives–chlordiazepoxide, diazepam, and phenobarbital; (4) antigout–allopurinol, colchicine, and probenecid; (5) antiarrhythmics–procainamide, propranolol (see WARNINGS however), and quinidine; and (6) analgesics, antipyretics and anti-inflammatories–propoxyphene, aspirin, indomethacin, and phenylbutazone. (Prazosin label, Drug interactions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

Strong Inhibitors of CYP2D6 The impact on the efficacy of tamoxifen with co-administration of strong CYP2D6 inhibitors (e.g., paroxetine) is not well established. (Tamoxifen label, Drug interactions)

Other Experience concerning injection of quinidine during recovery from use of other muscle relaxants suggests that recurrent paralysis may occur. (Vecuronium label, Precautions)

Digoxin Quinidine is an inhibitor of P-glycoprotein. (Dextromethorphan and quinidine label, Drug interactions)

Drugs Metabolized by Cytochrome P450 Isozymes In healthy subjects, a subcutaneous dose of 0.3 mg/kg of RELISTOR did not significantly affect the metabolism of dextromethorphan, a CYP2D6 substrate. (Methylnaltrexone label, Drug interactions)