Fesoterodine and Mirabegron interaction
Fesoterodine and Mirabegron: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Fesoterodine (Toviaz) label · effective 2026-04-07
CYP3A4 Inhibitors Doses of Toviaz greater than 4 mg are not recommended in adult patients taking strong CYP3A4 inhibitors, such as ketoconazole, itraconazole, and clarithromycin [see Dosage and Administration (2.5) ].
The Toviaz dose in pediatric patients taking strong CYP3A4 inhibitors is recommended to be reduced to 4 mg once daily in patients >35 kg and is not recommended in patients weighing greater than 25 kg and up to 35 kg [see Dosage and Administration (2.5) ].
Following blockade of CYP3A4 by coadministration of the moderate CYP3A4 inhibitor fluconazole 200 mg twice a day for 2 days, the average (90% confidence interval) increase in C max and AUC of the active metabolite of fesoterodine was approximately 19% (11%–28%) and 27% (18%–36%) respectively.
No dosing adjustments are recommended in the presence of moderate CYP3A4 inhibitors (e.g., erythromycin, fluconazole, diltiazem, verapamil and grapefruit juice).
In poor metabolizers for CYP2D6, representing a maximum CYP2D6 inhibition, C max and AUC of the active metabolite are increased 1.7- and 2-fold, respectively.
From the Mirabegron (Myrbetriq) label · effective 2024-08-01
• Urinary Retention in Patients With Bladder Outlet Obstruction and in Patients Taking Muscarinic Antagonist Drugs for Overactive Bladder : Administer with caution in these patients because of risk of urinary retention.
MYRBETRIQ should also be administered with caution to patients taking muscarinic antagonist medications for the treatment of OAB, including solifenacin succinate [see Clinical Pharmacology ( 12.2 )] .
Urinary Retention in Patients with Bladder Outlet Obstruction and in Patients Taking Muscarinic Antagonist Medications for OAB In patients taking MYRBETRIQ, urinary retention has been reported to occur in patients with bladder outlet obstruction (BOO) and in patients taking muscarinic antagonist medications for the treatment of OAB.
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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.