Drug interactions
Lumacaftor / ivacaftor + Zafirlukast
Severity: Moderate
Lumacaftor / ivacaftor 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 is cleared mainly by CYP2C9 and CYP3A4. Lumacaftor/ivacaftor has mixed effects on CYP2C9, with in vitro data suggesting induction by lumacaftor and inhibition by ivacaftor. Zafirlukast exposure could therefore rise or fall unpredictably.
What this interaction means in plain words
Lumacaftor / ivacaftor 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.
Why it happens
Lumacaftor may induce and ivacaftor may inhibit CYP2C9, so net effect on zafirlukast metabolism is uncertain (lumacaftor also induces CYP3A4).
What to do
Monitor asthma control and zafirlukast tolerability (including liver function if symptoms arise) after starting or stopping lumacaftor/ivacaftor. Adjust zafirlukast dose if loss of efficacy or adverse effects emerge.
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
Frequently asked questions
Can I take Lumacaftor / ivacaftor with Zafirlukast?
MediHelp rates the interaction as moderate. Lumacaftor / ivacaftor 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 is cleared mainly by CYP2C9 and CYP3A4. Lumacaftor/ivacaftor has mixed effects on CYP2C9, with in vitro data suggesting induction by lumacaftor and inhibition by ivacaftor. Zafirlukast exposure could therefore rise or fall unpredictably.
How serious is the interaction between Lumacaftor / ivacaftor 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 asthma control and zafirlukast tolerability (including liver function if symptoms arise) after starting or stopping lumacaftor/ivacaftor. Adjust zafirlukast dose if loss of efficacy or adverse effects emerge.
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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