Drug interactions
Darifenacin + Fosamprenavir
Severity: Major
Darifenacin 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 boosted with ritonavir, inhibits CYP3A4 and can raise darifenacin levels, increasing anticholinergic toxicity risk.
What this interaction means in plain words
Darifenacin 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
Inhibition of CYP3A4 by amprenavir reduces darifenacin clearance.
What to do
Do not exceed darifenacin 7.5 mg daily and monitor for anticholinergic toxicity. Consider an alternative agent.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Darifenacin and Fosamprenavir, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Darifenacin
Frequently asked questions
Can I take Darifenacin with Fosamprenavir?
MediHelp rates the interaction as major. Darifenacin 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 boosted with ritonavir, inhibits CYP3A4 and can raise darifenacin levels, increasing anticholinergic toxicity risk.
How serious is the interaction between Darifenacin 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: Do not exceed darifenacin 7.5 mg daily and monitor for anticholinergic toxicity. Consider an alternative agent.
What other medicines interact with Darifenacin?
MediHelp also lists interactions of Darifenacin with, for example, Atazanavir, Bethanechol, Clarithromycin. The full list is on the Darifenacin page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
