Drug interactions
Tolterodine + Zafirlukast
Severity: Minor
Tolterodine and Zafirlukast: minor 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
Tolterodine is metabolized by CYP2D6 and, in poor metabolizers, by CYP3A4. Zafirlukast may increase exposure mainly in CYP2D6 poor metabolizers, raising anticholinergic effects and QT risk.
What this interaction means in plain words
Tolterodine and Zafirlukast have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Tolterodine belongs to Genitourinary; Zafirlukast belongs to Respiratory.
Why it happens
Weak inhibition of CYP3A4-mediated tolterodine metabolism by zafirlukast.
What to do
Monitor for anticholinergic effects and consider a lower tolterodine dose if they occur, particularly in known CYP2D6 poor metabolizers.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Zafirlukast
- Pimozide + Zafirlukast Contraindicated
- Lomitapide + Zafirlukast Major
- Nilotinib + Zafirlukast Major
- Warfarin + Zafirlukast Major
- Apalutamide + Zafirlukast Moderate
- Carbamazepine + Zafirlukast Moderate
Other interactions of Tolterodine
Frequently asked questions
Can I take Tolterodine with Zafirlukast?
MediHelp rates the interaction as minor. Tolterodine and Zafirlukast have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Tolterodine is metabolized by CYP2D6 and, in poor metabolizers, by CYP3A4. Zafirlukast may increase exposure mainly in CYP2D6 poor metabolizers, raising anticholinergic effects and QT risk.
How serious is the interaction between Tolterodine and Zafirlukast?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for anticholinergic effects and consider a lower tolterodine dose if they occur, particularly in known CYP2D6 poor metabolizers.
What other medicines interact with Zafirlukast?
MediHelp also lists interactions of Zafirlukast with, for example, Pimozide, Lomitapide, Nilotinib. The full list is on the Zafirlukast page.
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