Drug interactions
Crizotinib + Fosamprenavir
Severity: Major
Crizotinib and Fosamprenavir: major 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
Fosamprenavir (amprenavir), especially when ritonavir-boosted, inhibits CYP3A4 and may substantially raise crizotinib levels. Crizotinib may also increase amprenavir exposure. Toxicities include hepatotoxicity, bradycardia and QT prolongation.
What this interaction means in plain words
Crizotinib and Fosamprenavir 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
CYP3A4 inhibition by amprenavir reduces crizotinib clearance, and crizotinib inhibits CYP3A4 and possibly P-gp.
What to do
Avoid the combination where possible. If used, reduce the crizotinib dose per labeling and monitor ECG and liver tests.
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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Other interactions of Crizotinib
- Crizotinib + Flibanserin Contraindicated
- Crizotinib + Lomitapide Contraindicated
- Crizotinib + Lonafarnib Contraindicated
- Crizotinib + Pimozide Contraindicated
- Crizotinib + Saquinavir Contraindicated
- Crizotinib + Thioridazine Contraindicated
Frequently asked questions
Can I take Crizotinib with Fosamprenavir?
MediHelp rates the interaction as major. Crizotinib and Fosamprenavir 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. Fosamprenavir (amprenavir), especially when ritonavir-boosted, inhibits CYP3A4 and may substantially raise crizotinib levels. Crizotinib may also increase amprenavir exposure. Toxicities include hepatotoxicity, bradycardia and QT prolongation.
How serious is the interaction between Crizotinib and Fosamprenavir?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible. If used, reduce the crizotinib dose per labeling and monitor ECG and liver tests.
What other medicines interact with Crizotinib?
MediHelp also lists interactions of Crizotinib with, for example, Flibanserin, Lomitapide, Lonafarnib. The full list is on the Crizotinib page.
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