Drug interactions
Quinidine + Tolterodine
Severity: Major
Quinidine 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
Quinidine is a potent CYP2D6 inhibitor that effectively makes patients poor metabolizers, raising tolterodine exposure. The active metabolite falls but total active moiety is mostly maintained. Quinidine also prolongs QT and has anticholinergic properties.
What this interaction means in plain words
Quinidine 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.
Quinidine belongs to Anti Parasitic; Tolterodine belongs to Genitourinary.
Why it happens
Potent CYP2D6 inhibition by quinidine, with additive QT prolongation.
What to do
Monitor the ECG and anticholinergic effects, and consider a tolterodine dose reduction. Prefer a different antimuscarinic if QTc is borderline.
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 Tolterodine
Other interactions of Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Frequently asked questions
Can I take Quinidine with Tolterodine?
MediHelp rates the interaction as major. Quinidine 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. Quinidine is a potent CYP2D6 inhibitor that effectively makes patients poor metabolizers, raising tolterodine exposure. The active metabolite falls but total active moiety is mostly maintained. Quinidine also prolongs QT and has anticholinergic properties.
How serious is the interaction between Quinidine 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: Monitor the ECG and anticholinergic effects, and consider a tolterodine dose reduction. Prefer a different antimuscarinic if QTc is borderline.
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.
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