Drug interactions
Erythromycin base + Tolterodine
Severity: Major
Erythromycin base 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
Erythromycin inhibits CYP3A4 and can raise tolterodine levels, particularly in CYP2D6 poor metabolizers. Both drugs can prolong the QT interval, so arrhythmia risk is also increased.
What this interaction means in plain words
Erythromycin base 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.
Why it happens
CYP3A4 inhibition reduces tolterodine clearance, with additive QT prolongation.
What to do
Limit tolterodine to 2 mg daily and monitor ECG if the combination is needed, or use a non-interacting antibiotic such as azithromycin with caution.
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
Frequently asked questions
Can I take Erythromycin base with Tolterodine?
MediHelp rates the interaction as major. Erythromycin base 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. Erythromycin inhibits CYP3A4 and can raise tolterodine levels, particularly in CYP2D6 poor metabolizers. Both drugs can prolong the QT interval, so arrhythmia risk is also increased.
How serious is the interaction between Erythromycin base 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 and monitor ECG if the combination is needed, or use a non-interacting antibiotic such as azithromycin with caution.
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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