Drug interactions
Ketoconazole + Nirmatrelvir
Severity: Moderate
Ketoconazole and Nirmatrelvir: 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
Nirmatrelvir is given with ritonavir, a strong CYP3A4 inhibitor, which increases ketoconazole concentrations. Higher ketoconazole levels may increase hepatotoxicity and QT prolongation risk.
What this interaction means in plain words
Ketoconazole and Nirmatrelvir 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.
Ketoconazole belongs to Anti Fungals; Nirmatrelvir belongs to Anti Virals.
Why it happens
Ritonavir-boosted CYP3A4 inhibition reduces ketoconazole metabolism.
What to do
Limit ketoconazole to 200 mg/day during co-therapy and monitor for ketoconazole adverse effects including liver function.
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 Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Other interactions of Nirmatrelvir
- Alfuzosin + Nirmatrelvir Contraindicated
- Amiodarone + Nirmatrelvir Contraindicated
- Apalutamide + Nirmatrelvir Contraindicated
- Carbamazepine + Nirmatrelvir Contraindicated
- Colchicine + Nirmatrelvir Contraindicated
- Dronedarone + Nirmatrelvir Contraindicated
Frequently asked questions
Can I take Ketoconazole with Nirmatrelvir?
MediHelp rates the interaction as moderate. Ketoconazole and Nirmatrelvir 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. Nirmatrelvir is given with ritonavir, a strong CYP3A4 inhibitor, which increases ketoconazole concentrations. Higher ketoconazole levels may increase hepatotoxicity and QT prolongation risk.
How serious is the interaction between Ketoconazole and Nirmatrelvir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Limit ketoconazole to 200 mg/day during co-therapy and monitor for ketoconazole adverse effects including liver function.
What other medicines interact with Ketoconazole?
MediHelp also lists interactions of Ketoconazole with, for example, Alfuzosin, Alprazolam, Avanafil. The full list is on the Ketoconazole page.
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