Drug interactions
Ketoconazole + Tolterodine
Severity: Major
Ketoconazole and Tolterodine: 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
Ketoconazole substantially increases tolterodine exposure through CYP3A4 inhibition, notably in CYP2D6 poor metabolizers. This increases anticholinergic adverse effects and potential QT prolongation.
What this interaction means in plain words
Ketoconazole and Tolterodine 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.
Ketoconazole belongs to Anti Fungals; Tolterodine belongs to Genitourinary.
Why it happens
Strong CYP3A4 inhibition by ketoconazole decreases tolterodine metabolism.
What to do
Limit tolterodine to 2 mg daily (1 mg twice daily for the IR tablet), or choose another antifungal; monitor for anticholinergic effects and ECG changes if risk factors exist.
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 Ketoconazole and Tolterodine, 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 14 days on the web. No card needed.
Other interactions of Tolterodine
Other interactions of Ketoconazole
- Alfuzosin + Ketoconazole Contraindicated
- Alprazolam + Ketoconazole Contraindicated
- Avanafil + Ketoconazole Contraindicated
- Conivaptan + Ketoconazole Contraindicated
- Dihydroergotamine intranasal + Ketoconazole Contraindicated
- Dihydroergotamine + Ketoconazole Contraindicated
Frequently asked questions
Can I take Ketoconazole with Tolterodine?
MediHelp rates the interaction as major. Ketoconazole and Tolterodine 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. Ketoconazole substantially increases tolterodine exposure through CYP3A4 inhibition, notably in CYP2D6 poor metabolizers. This increases anticholinergic adverse effects and potential QT prolongation.
How serious is the interaction between Ketoconazole and Tolterodine?
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 tolterodine to 2 mg daily (1 mg twice daily for the IR tablet), or choose another antifungal; monitor for anticholinergic effects and ECG changes if risk factors exist.
What other medicines interact with Tolterodine?
MediHelp also lists interactions of Tolterodine with, for example, Clarithromycin, Clozapine, Cobicistat. The full list is on the Tolterodine 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.
