Drug interactions
Fosamprenavir + Ketoconazole
Severity: Major
Fosamprenavir and Ketoconazole: major interaction.
Last updated Sources: US FDA label
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
Ketoconazole raises amprenavir levels and amprenavir raises ketoconazole levels. This increases the risk of adverse effects from both drugs.
What this interaction means in plain words
Fosamprenavir and Ketoconazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Reciprocal CYP3A4 inhibition.
What to do
Reduce the ketoconazole dose when it exceeds 400 mg daily, and avoid doses over 200 mg daily with ritonavir-boosted fosamprenavir. Monitor for toxicity and liver function.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
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 Fosamprenavir with Ketoconazole?
MediHelp rates the interaction as major. Fosamprenavir and Ketoconazole can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Ketoconazole raises amprenavir levels and amprenavir raises ketoconazole levels. This increases the risk of adverse effects from both drugs.
How serious is the interaction between Fosamprenavir and Ketoconazole?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Reduce the ketoconazole dose when it exceeds 400 mg daily, and avoid doses over 200 mg daily with ritonavir-boosted fosamprenavir. Monitor for toxicity and 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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