Drug interactions
Metronidazole + Ritonavir
Severity: Moderate
Metronidazole and Ritonavir: 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
Ritonavir oral solution contains ethanol, and metronidazole can cause a disulfiram-like reaction with alcohol. Patients may develop flushing, nausea, vomiting and palpitations. Ritonavir itself is not meaningfully affected by metronidazole through CYP3A4.
What this interaction means in plain words
Metronidazole and Ritonavir 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; Ritonavir belongs to Anti Virals.
Why it happens
Ethanol in the ritonavir formulation combined with metronidazole's inhibition of aldehyde dehydrogenase-mediated acetaldehyde clearance (proposed mechanism).
What to do
Prefer ritonavir tablets or capsules over the ethanol-containing oral solution during metronidazole therapy. If the solution is required, counsel the patient about symptoms and monitor for flushing, nausea and tachycardia.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Metronidazole and Ritonavir, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
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 Ritonavir
- Alfuzosin + Ritonavir Contraindicated
- Amiodarone + Ritonavir Contraindicated
- Avanafil + Ritonavir Contraindicated
- Colchicine + Ritonavir Contraindicated
- Dronedarone + Ritonavir Contraindicated
- Eletriptan + Ritonavir Contraindicated
Frequently asked questions
Can I take Metronidazole with Ritonavir?
MediHelp rates the interaction as moderate. Metronidazole and Ritonavir 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. Ritonavir oral solution contains ethanol, and metronidazole can cause a disulfiram-like reaction with alcohol. Patients may develop flushing, nausea, vomiting and palpitations. Ritonavir itself is not meaningfully affected by metronidazole through CYP3A4.
How serious is the interaction between Metronidazole and Ritonavir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer ritonavir tablets or capsules over the ethanol-containing oral solution during metronidazole therapy. If the solution is required, counsel the patient about symptoms and monitor for flushing, nausea and tachycardia.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
