Drug interactions
Isoniazid + Ritonavir
Severity: Moderate
Isoniazid 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
Isoniazid is only a weak CYP3A4 inhibitor, and ritonavir is itself a potent CYP3A4 inhibitor, so any pharmacokinetic effect is trivial. Both can be hepatotoxic, so combined liver injury is the practical concern.
What this interaction means in plain words
Isoniazid 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.
Isoniazid belongs to Anti Bacterial; Ritonavir belongs to Anti Virals.
Why it happens
Additive hepatotoxicity; negligible CYP3A4 effect of isoniazid on ritonavir.
What to do
Monitor liver function tests regularly during combined antituberculosis and antiretroviral therapy. Stop or modify treatment if transaminases rise significantly or hepatitis symptoms appear.
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 Isoniazid
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 Isoniazid with Ritonavir?
MediHelp rates the interaction as moderate. Isoniazid 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. Isoniazid is only a weak CYP3A4 inhibitor, and ritonavir is itself a potent CYP3A4 inhibitor, so any pharmacokinetic effect is trivial. Both can be hepatotoxic, so combined liver injury is the practical concern.
How serious is the interaction between Isoniazid 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: Monitor liver function tests regularly during combined antituberculosis and antiretroviral therapy. Stop or modify treatment if transaminases rise significantly or hepatitis symptoms appear.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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