Drug interactions
Darifenacin + Elvitegravir / cobicistat / emtricitabine / tenofovir df
Severity: Major
Darifenacin and Elvitegravir / cobicistat / emtricitabine / tenofovir df: 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
Cobicistat is a strong CYP3A4 inhibitor and can substantially increase exposure to darifenacin, which is cleared mainly by CYP3A4 and CYP2D6. This raises the risk of anticholinergic adverse effects such as dry mouth, constipation, urinary retention and blurred vision. Darifenacin labeling limits the dose with potent CYP3A4 inhibitors.
What this interaction means in plain words
Darifenacin and Elvitegravir / cobicistat / emtricitabine / tenofovir df 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
Cobicistat inhibits CYP3A4 (intestinal and hepatic), reducing darifenacin clearance.
What to do
Limit darifenacin to 7.5 mg daily with a strong CYP3A4 inhibitor and monitor for anticholinergic toxicity. Consider an alternative bladder agent if effects are not tolerated.
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 Darifenacin
Frequently asked questions
Can I take Darifenacin with Elvitegravir / cobicistat / emtricitabine / tenofovir df?
MediHelp rates the interaction as major. Darifenacin and Elvitegravir / cobicistat / emtricitabine / tenofovir df 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. Cobicistat is a strong CYP3A4 inhibitor and can substantially increase exposure to darifenacin, which is cleared mainly by CYP3A4 and CYP2D6. This raises the risk of anticholinergic adverse effects such as dry mouth, constipation, urinary retention and blurred vision. Darifenacin labeling limits the dose with potent CYP3A4 inhibitors.
How serious is the interaction between Darifenacin and Elvitegravir / cobicistat / emtricitabine / tenofovir df?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Limit darifenacin to 7.5 mg daily with a strong CYP3A4 inhibitor and monitor for anticholinergic toxicity. Consider an alternative bladder agent if effects are not tolerated.
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.
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