Drug interactions
Metronidazole + Quinidine
Severity: Moderate
Metronidazole and Quinidine: 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
Quinidine is metabolized by CYP3A4 and has a narrow therapeutic index with significant QT prolongation and proarrhythmia risk. Metronidazole may modestly raise levels and also has rare QT effects, so additive risk is conceivable.
What this interaction means in plain words
Metronidazole and Quinidine 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 belongs to Anti Parasitic; Quinidine belongs to Anti Parasitic.
Why it happens
Possible weak CYP3A4 inhibition by metronidazole reducing quinidine clearance, with additive QT effects.
What to do
Monitor ECG (QTc) and quinidine levels, and correct potassium and magnesium. Consider an alternative antibiotic if QTc prolongs.
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 Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Frequently asked questions
Can I take Metronidazole with Quinidine?
MediHelp rates the interaction as moderate. Metronidazole and Quinidine 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. Quinidine is metabolized by CYP3A4 and has a narrow therapeutic index with significant QT prolongation and proarrhythmia risk. Metronidazole may modestly raise levels and also has rare QT effects, so additive risk is conceivable.
How serious is the interaction between Metronidazole and Quinidine?
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 ECG (QTc) and quinidine levels, and correct potassium and magnesium. Consider an alternative antibiotic if QTc prolongs.
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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