Ketoconazole and Tolterodine interaction
Ketoconazole and Tolterodine: 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 Ketoconazole label · effective 2026-07-07
Respiratory Drugs salmeterol Urological Drugs fesoterodine, sildenafil, solifenacin, tadalafil, tolterodine, vardenafil Vardenafil: A single dose of 5 mg of vardenafil should not be exceeded when coadministered with ketoconazole.
From the Tolterodine (Detrol) label · effective 2023-02-15
Drug Interactions CYP3A4 Inhibitors Ketoconazole, an inhibitor of the drug metabolizing enzyme CYP3A4, significantly increased plasma concentrations of tolterodine when coadministered to subjects who were poor metabolizers (see CLINICAL PHARMACOLOGY, Variability in Metabolism and Drug-Drug Interactions ).
For patients receiving ketoconazole or other potent CYP3A4 inhibitors such as other azole antifungals (e.g., itraconazole, miconazole) or macrolide antibiotics (e.g., erythromycin, clarithromycin) or cyclosporine or vinblastine, the recommended dose of DETROL is 1 mg twice daily (see DOSAGE AND ADMINISTRATION ).
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.