Drug interactions
Siponimod + Zafirlukast
Severity: Moderate
Siponimod and Zafirlukast: moderate 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
Zafirlukast inhibits CYP2C9 in vitro and could raise siponimod exposure, since siponimod is cleared mainly by CYP2C9 with a minor CYP3A4 contribution. Higher siponimod levels may increase bradycardia, conduction effects, lymphopenia and infection risk.
What this interaction means in plain words
Siponimod and Zafirlukast can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Siponimod belongs to Central Nervous System; Zafirlukast belongs to Respiratory.
Why it happens
Inhibition of CYP2C9-mediated siponimod metabolism by zafirlukast.
What to do
Monitor heart rate and lymphocyte counts, especially after starting zafirlukast in a patient on siponimod. Consider an alternative leukotriene antagonist such as montelukast if exposure concerns arise.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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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 Siponimod
- Cladribine + Siponimod Contraindicated
- Fingolimod + Siponimod Contraindicated
- Fluconazole + Siponimod Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Siponimod Contraindicated
- Ponesimod + Siponimod Contraindicated
- Siponimod + Thioridazine Contraindicated
Frequently asked questions
Can I take Siponimod with Zafirlukast?
MediHelp rates the interaction as moderate. Siponimod and Zafirlukast can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Zafirlukast inhibits CYP2C9 in vitro and could raise siponimod exposure, since siponimod is cleared mainly by CYP2C9 with a minor CYP3A4 contribution. Higher siponimod levels may increase bradycardia, conduction effects, lymphopenia and infection risk.
How serious is the interaction between Siponimod and Zafirlukast?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor heart rate and lymphocyte counts, especially after starting zafirlukast in a patient on siponimod. Consider an alternative leukotriene antagonist such as montelukast if exposure concerns arise.
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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