Drug interactions
Fesoterodine + Fosamprenavir
Severity: Moderate
Fesoterodine and Fosamprenavir: 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
Amprenavir, the active form of fosamprenavir, inhibits CYP3A4, particularly when boosted with ritonavir. Exposure to the active metabolite of fesoterodine may rise and increase anticholinergic adverse effects.
What this interaction means in plain words
Fesoterodine and Fosamprenavir 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
Inhibition of CYP3A4 reduces clearance of the active metabolite of fesoterodine.
What to do
Do not exceed fesoterodine 4 mg daily with potent CYP3A4 inhibitors, and monitor for anticholinergic effects.
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 Fesoterodine
Frequently asked questions
Can I take Fesoterodine with Fosamprenavir?
MediHelp rates the interaction as moderate. Fesoterodine and Fosamprenavir 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. Amprenavir, the active form of fosamprenavir, inhibits CYP3A4, particularly when boosted with ritonavir. Exposure to the active metabolite of fesoterodine may rise and increase anticholinergic adverse effects.
How serious is the interaction between Fesoterodine and Fosamprenavir?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Do not exceed fesoterodine 4 mg daily with potent CYP3A4 inhibitors, and monitor for anticholinergic effects.
What other medicines interact with Fesoterodine?
MediHelp also lists interactions of Fesoterodine with, for example, Bethanechol, Clozapine, Levoketoconazole. The full list is on the Fesoterodine page.
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