Drug interactions
Fosamprenavir + Warfarin
Severity: Moderate
Fosamprenavir and Warfarin: 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
Fosamprenavir, converted to amprenavir, is a boosted protease inhibitor with mixed inhibitory and inducing effects on enzymes. Warfarin exposure can fall or rise unpredictably, so INR may drift out of range.
What this interaction means in plain words
Fosamprenavir and Warfarin 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
Mixed CYP inhibition and induction, with net effect on warfarin metabolism variable.
What to do
Monitor INR closely when starting, stopping or changing the antiretroviral regimen. Adjust warfarin dosing to maintain the target range.
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 Warfarin
- Defibrotide + Warfarin Contraindicated
- Ketorolac + Warfarin Contraindicated
- Abciximab + Warfarin Major
- Acetylsalicylic acid + Warfarin Major
- Adagrasib + Warfarin Major
- Amiodarone + Warfarin Major
Frequently asked questions
Can I take Fosamprenavir with Warfarin?
MediHelp rates the interaction as moderate. Fosamprenavir and Warfarin 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. Fosamprenavir, converted to amprenavir, is a boosted protease inhibitor with mixed inhibitory and inducing effects on enzymes. Warfarin exposure can fall or rise unpredictably, so INR may drift out of range.
How serious is the interaction between Fosamprenavir and Warfarin?
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 INR closely when starting, stopping or changing the antiretroviral regimen. Adjust warfarin dosing to maintain the target range.
What other medicines interact with Warfarin?
MediHelp also lists interactions of Warfarin with, for example, Defibrotide, Ketorolac, Abciximab. The full list is on the Warfarin page.
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