Drug interactions
Tamoxifen + Zafirlukast
Severity: Minor
Tamoxifen 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
Tamoxifen is activated to endoxifen mainly by CYP2D6, with CYP3A4 and CYP2C9 contributing to other pathways. The legacy rationale of reduced activation through CYP2C9 inhibition is weak, and the clinical effect on efficacy is unproven.
What this interaction means in plain words
Tamoxifen 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.
Tamoxifen belongs to Endocrine; Zafirlukast belongs to Respiratory.
Why it happens
Possible minor inhibition of CYP2C9 and CYP3A4 pathways of tamoxifen metabolism by zafirlukast; clinical significance is not established.
What to do
No dose change is required. Be aware of the theoretical effect and avoid adding strong CYP2D6 inhibitors.
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 Tamoxifen
- Amiodarone + Tamoxifen Major
- Anastrozole + Tamoxifen Major
- Bupropion + Tamoxifen Major
- Carbamazepine + Tamoxifen Major
- Cinacalcet + Tamoxifen Major
- Dacomitinib + Tamoxifen Major
Frequently asked questions
Can I take Tamoxifen with Zafirlukast?
MediHelp rates the interaction as minor. Tamoxifen 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. Tamoxifen is activated to endoxifen mainly by CYP2D6, with CYP3A4 and CYP2C9 contributing to other pathways. The legacy rationale of reduced activation through CYP2C9 inhibition is weak, and the clinical effect on efficacy is unproven.
How serious is the interaction between Tamoxifen 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 required. Be aware of the theoretical effect and avoid adding strong CYP2D6 inhibitors.
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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