Drug interactions
Fesoterodine + Zafirlukast
Severity: Minor
Fesoterodine 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
Fesoterodine is converted to the active 5-hydroxymethyl tolterodine, which is cleared by CYP3A4 and CYP2D6. Zafirlukast is a weak CYP3A4 inhibitor, so any increase in anticholinergic effects is likely small.
What this interaction means in plain words
Fesoterodine 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.
Fesoterodine belongs to Genitourinary; Zafirlukast belongs to Respiratory.
Why it happens
Weak CYP3A4 inhibition by zafirlukast may slightly reduce clearance of the active fesoterodine metabolite.
What to do
No dose change is needed. Monitor for dry mouth, constipation and urinary retention.
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 Fesoterodine
Frequently asked questions
Can I take Fesoterodine with Zafirlukast?
MediHelp rates the interaction as minor. Fesoterodine 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. Fesoterodine is converted to the active 5-hydroxymethyl tolterodine, which is cleared by CYP3A4 and CYP2D6. Zafirlukast is a weak CYP3A4 inhibitor, so any increase in anticholinergic effects is likely small.
How serious is the interaction between Fesoterodine 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: No dose change is needed. Monitor for dry mouth, constipation and urinary retention.
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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