Darifenacin and Nirmatrelvir and ritonavir interaction
Darifenacin and Nirmatrelvir and ritonavir: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Darifenacin label · effective 2026-02-10
CYP3A4 Inhibitors The systemic exposure of darifenacin from darifenacin extended-release tablets is increased in the presence of CYP3A4 inhibitors.
The daily dose of darifenacin extended-release tablets should not exceed 7.5 mg when co-administered with potent CYP3A4 inhibitors (for example, ketoconazole, itraconazole, ritonavir, nelfinavir, clarithromycin and nefazadone).
No dosing adjustments are recommended in the presence of moderate CYP3A4 inhibitors (for example, erythromycin, fluconazole, diltiazem and verapamil) [see Dosage and Administration (2) and Clinical Pharmacology (12.3)] .
From the Nirmatrelvir and ritonavir (Paxlovid) label · effective 2026-02-19
Muscarinic receptor antagonists darifenacin ↑ darifenacin The darifenacin daily-dose should not exceed 7.5 mg when co-administered with PAXLOVID.
Refer to the darifenacin prescribing information for more information.
Potential for PAXLOVID to Affect Other Drugs PAXLOVID (nirmatrelvir co-packaged with ritonavir) is a strong inhibitor of CYP3A, and an inhibitor of CYP2D6, P-gp and OATP1B1.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.