Drug interactions
Fluorouracil + Metronidazole
Severity: Moderate
Fluorouracil and Metronidazole: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Metronidazole has been reported to raise systemic fluorouracil exposure, which can increase myelosuppression, mucositis, diarrhea and other fluorouracil toxicities. The effect is based on limited pharmacokinetic and clinical data but matters because of the narrow therapeutic index of fluorouracil.
What this interaction means in plain words
Fluorouracil and Metronidazole can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fluorouracil belongs to Oncology; Metronidazole belongs to Anti Parasitic.
Why it happens
Metronidazole appears to reduce the clearance of fluorouracil, although the exact mechanism is not firmly established.
What to do
Monitor blood counts and signs of mucositis, diarrhea and hand-foot syndrome when metronidazole is given during fluorouracil therapy. Reduce or hold fluorouracil if toxicity develops, and use an alternative antimicrobial if feasible.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Metronidazole
- Ethanol + Metronidazole Contraindicated
- Metronidazole + Pimozide Contraindicated
- Amiodarone + Metronidazole Major
- Disulfiram + Metronidazole Major
- Ergotamine + Metronidazole Major
- Lomitapide + Metronidazole Major
Other interactions of Fluorouracil
Frequently asked questions
Can I take Fluorouracil with Metronidazole?
MediHelp rates the interaction as moderate. Fluorouracil and Metronidazole can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Metronidazole has been reported to raise systemic fluorouracil exposure, which can increase myelosuppression, mucositis, diarrhea and other fluorouracil toxicities. The effect is based on limited pharmacokinetic and clinical data but matters because of the narrow therapeutic index of fluorouracil.
How serious is the interaction between Fluorouracil and Metronidazole?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor blood counts and signs of mucositis, diarrhea and hand-foot syndrome when metronidazole is given during fluorouracil therapy. Reduce or hold fluorouracil if toxicity develops, and use an alternative antimicrobial if feasible.
What other medicines interact with Metronidazole?
MediHelp also lists interactions of Metronidazole with, for example, Ethanol, Pimozide, Amiodarone. The full list is on the Metronidazole page.
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