Fluorouracil interactions
Fluorouracil (Adrucil, Efudex, Carac), an antimetabolite has 45 documented interactions across the FDA labels and fact sheets we index: 6 major, 29 moderate, 10 minor, and 0 where a label reports no significant interaction. Each entry below quotes the sentence behind it. This drug page is a starting point, not a verdict for your situation.
Interactions from the label
Major interactions (6)
Intervention Concomitant administration with fluorouracil should be avoided. (Allopurinol label, Drug interactions)
Co-administration of such combinations of a CYP2C9 inhibitor plus a strong or moderate CYP3A inhibitor with TRACLEER is not recommended. (Bosentan label, Drug interactions)
XELODA is contraindicated in patients with history of severe hypersensitivity reaction to fluorouracil or capecitabine [see Adverse Reactions (6.1) ] . (Capecitabine label, Contraindications)
- LevoleucovorinMajor
Deaths from severe enterocolitis, diarrhea, and dehydration have occurred in elderly patients receiving weekly d,l- leucovorin and fluorouracil. (Levoleucovorin label, Warnings and precautions)
- MacitentanMajor
Moderate dual CYP3A4 and CYP2C9 inhibitors (fluconazole, amiodarone) or use of combined CYP3A4 and CYP2C9 inhibitors may increase exposure to macitentan: avoid co-administration with OPSUMIT ( 7.3 , 12.3 ). (Macitentan label, Drug interactions)
If the concomitant use of tinidazole and fluorouracil cannot be avoided, the patient should be monitored for fluorouracilassociated toxicities. (Tinidazole label, Drug interactions)
Moderate interactions (29)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
HIV Protease inhibitor — Ritonavir (600 mg twice daily), a strong CYP3A4 inhibitor, which also inhibits CYP2C9, increased avanafil 50 mg single-dose C max and AUC equal to approximately 2-fold and 13-fold, and prolonged the half-life of avanafil to approximately 9 hours in healthy volunteers. (Avanafil label, Drug interactions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Amiodarone Amiodarone and its metabolite desethyl amiodarone, inhibitors of CYP2C9, and P- glycoprotein increased concentrations of the S(-)-enantiomer of carvedilol by at least 2 fold [see Clinical Pharmacology (12.5) ]. (Carvedilol label, Drug interactions)
Co-administration of celecoxib with drugs that are known to inhibit CYP2C9 (e.g., fluconazole) may enhance the exposure and toxicity of celecoxib whereas co-administration with CYP2C9 inducers (e.g., rifampin) may lead to compromised efficacy of celecoxib. (Celecoxib label, Drug interactions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Co-administration of diclofenac with CYP2C9 inhibitors (e.g. voriconazole) may enhance the exposure and toxicity of diclofenac whereas co- administration with CYP2C9 inducers (e.g. rifampin) may lead to compromised efficacy of diclofenac. (Diclofenac label, Drug interactions)
Co-administration of diclofenac with CYP2C9 inhibitors (e.g., voriconazole) may enhance the exposure and toxicity of diclofenac [see Clinical Pharmacology (12.3) ] whereas co-administration with CYP2C9 inducers (e.g., rifampin) may lead to compromised efficacy of diclofenac. (Diclofenac and misoprostol label, Drug interactions)
Monitor for increased dronabinol-related adverse reactions when dronabinol oral solution is co-administered with inhibitors of CYP2C9 (e.g., amiodarone, fluconazole) and inhibitors of CYP3A4 enzymes (e.g., ketoconazole, itraconazole, clarithromycin, ritonavir, erythromycin, grapefruit juice). (Dronabinol label, Drug interactions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Effect of TRIKAFTA on Other Drugs CYP2C9 Substrates Ivacaftor may inhibit CYP2C9; therefore, monitoring of the international normalized ratio (INR) during concomitant use of TRIKAFTA with warfarin is recommended. (Elexacaftor, tezacaftor, and ivacaftor label, Drug interactions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
…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,… (Fosphenytoin label, Drug interactions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Strong CYP3A4 or CYP2C9 Inhibitors Patients with renal or hepatic impairment who are taking strong inhibitors of CYP3A4 and CYP2C9 may have a significant increase in exposure to VIMPAT. (Lacosamide label, Drug interactions)
…Drugs That May Alter T 4 and Triiodothyronine (T 3 ) Serum Transport Without Effecting Free Thyroxine (FT 4 ) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Levothyroxine label, Drug interactions)
Table 2: Drugs That May Alter Triiodothyronine (T3) Serum Transport Without Affecting Free Thyroxine (FT4) Concentration (Euthyroidism) Drug or Drug Class Effect Clofibrate Estrogen-containing oral contraceptives Estrogens (oral) Heroin/Methadone 5-Fluorouracil Mitotane Tamoxifen These drugs may increase serum thyroxine-binding globulin (TBG) concentration. (Liothyronine label, Drug interactions)
Thus concomitant usage of CYP2C9 inhibitors (such as amiodarone, fluconazole, and sulphaphenazole) may lead to abnormally high plasma levels of meloxicam due to reduced metabolic clearance [ see Use in Specific Populations ( 8.8 ); and Clinical Pharmacology ( 12.3 , 12.5 ) ]. (Meloxicam label, Drug interactions)
…salicylates, monoamine oxidase inhibitors, non-selective beta-adrenergic-blocking agents, anabolic hormones (e.g., methandrostenolone), guanethidine, gymnema sylvestre, glucomannan, thioctic acid, and inhibitors of CYP2C9 (e.g., amiodarone, fluconazole, voriconazole, sulfinpyrazone) or in patients known to be poor metabolizers of CYP2C9 substrates, alcohol. (Nateglinide label, Drug interactions)
- OxaliplatinModerate
Hemorrhage : Increase frequency of monitoring in patients who are receiving oxaliplatin injection with fluorouracil/leucovorin and oral anticoagulants (5.9) (Oxaliplatin label, Warnings and precautions)
…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)
Fluconazole (strong CYP2C9 inhibitor): Increases systemic exposure of ramelteon; administer with caution. (Ramelteon label, Drug interactions)
Closely monitor patients receiving concomitant coumarin-derivative anticoagulants such as warfarin for INR or prothrombin time in order to adjust the anticoagulant dose accordingly [see Drug Interactions (7) ]. (Fluorouracil label, Warnings and precautions)
Rosuvastatin plasma levels can be significantly increased with concomitant administration of inhibitors of CYP2C9 and transporters. (Rosuvastatin label, Drug interactions)
CYP2C9: Concomitant use with CYP2C9 inhibitors can decrease torsemide clearance. (Torsemide label, Drug interactions)
Increased Risk of Elevated INR with Warfarin: Concurrent administration with warfarin can result in clinically significant increases in coagulation parameters: Closely monitor INR and prothrombin time. (Fluorouracil label, Warnings and precautions)
Zafirlukast exposure is likely to be increased by other moderate and strong CYP2C9 inhibitors. (Zafirlukast label, Precautions)
Minor mentions (10)
However, at high concentrations in vitro , clopidogrel inhibits CYP2C9. (Clopidogrel label, Drug interactions)
- DexrazoxaneMinor
In a trial conducted in patients with metastatic breast cancer who were treated with fluorouracil, doxorubicin, and cyclophosphamide (FAC) with or without dexrazoxane starting with their first cycle of FAC therapy, patients who were randomized to receive dexrazoxane had a lower response rate (48% vs. 63%) and shorter time to progression than patients who were… (Dexrazoxane label, Warnings and precautions)
- DocetaxelMinor
In gastric cancer patients treated with docetaxel in combination with cisplatin and fluorouracil (TCF), febrile neutropenia and/or neutropenic infection occurred in 12% of patients receiving G-CSF compared to 28% who did not. (Docetaxel label, Warnings and precautions)
5-Fluorouracil is a metabolite of flucytosine. (Flucytosine label, Warnings)
- IrinotecanMinor
5-Fluorouracil (5-FU) and Leucovorin (LV) In a phase 1 clinical study involving irinotecan, 5-fluorouracil (5-FU), and leucovorin (LV) in 26 patients with solid tumors, the disposition of irinotecan was not substantially altered when the drugs were co-administered. (Irinotecan label, Drug interactions)
Oral neomycin inhibits the gastrointestinal absorption of penicillin V, oral vitamin B-12, methotrexate and 5-fluorouracil. (Neomycin label, Drug interactions)
Fluconazole is an inhibitor of CYP2C9 and CYP3A enzymes. (Terbinafine label, Drug interactions)
Toremifene is a weak inhibitor of CYP2C9. (Toremifene label, Drug interactions)
The interaction is a consequence of blocking hepatic metabolism of vardenafil by ritonavir, a HIV protease inhibitor and a highly strong CYP3A4 inhibitor, which also inhibits CYP2C9. (Vardenafil label, Drug interactions)
CYP2C9 Venlafaxine did not inhibit CYP2C9 in vitro . (Venlafaxine label, Drug interactions)
Check Fluorouracil against everything you take. Add your full list; every pair is checked at once.
Open in the checkerNot medical advice. Severity reflects the label's wording, not your circumstances. A "major" flag can be routine under supervision and a "minor" one can matter at high doses. Ask a pharmacist.