Drug interactions
Ketoconazole + Nirmatrelvir / ritonavir
Severity: Moderate
Ketoconazole and Nirmatrelvir / 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 inhibits CYP3A4 and increases ketoconazole exposure, while ketoconazole may also raise ritonavir and nirmatrelvir levels. This raises the risk of hepatotoxicity and QT prolongation.
What this interaction means in plain words
Ketoconazole and Nirmatrelvir / 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.
Why it happens
Mutual CYP3A4 inhibition, with ritonavir reducing ketoconazole clearance.
What to do
Limit ketoconazole to 200 mg/day and monitor for adverse effects, including liver tests and ECG if risk factors exist.
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
Frequently asked questions
Can I take Ketoconazole with Nirmatrelvir / ritonavir?
MediHelp rates the interaction as moderate. Ketoconazole and Nirmatrelvir / 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 inhibits CYP3A4 and increases ketoconazole exposure, while ketoconazole may also raise ritonavir and nirmatrelvir levels. This raises the risk of hepatotoxicity and QT prolongation.
How serious is the interaction between Ketoconazole and Nirmatrelvir / 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: Limit ketoconazole to 200 mg/day and monitor for adverse effects, including liver tests and ECG if risk factors exist.
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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