Drug interactions
Lapatinib + Zafirlukast
Severity: Moderate
Lapatinib 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
Lapatinib is a CYP3A4 substrate, and zafirlukast may modestly increase its exposure. Higher lapatinib levels could increase diarrhea, rash, hepatotoxicity and QT prolongation.
What this interaction means in plain words
Lapatinib 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.
Lapatinib belongs to Oncology; Zafirlukast belongs to Respiratory.
Why it happens
Inhibition of CYP3A4-mediated lapatinib metabolism by zafirlukast.
What to do
Monitor liver function and watch for diarrhea and QT-related symptoms, with an ECG if risk factors are present. Reduce the lapatinib dose or choose an alternative to zafirlukast if toxicity develops.
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 Lapatinib
- Dofetilide + Lapatinib Contraindicated
- Ibutilide + Lapatinib Contraindicated
- Lapatinib + Pimozide Contraindicated
- Lapatinib + Saquinavir Contraindicated
- Lapatinib + Thioridazine Contraindicated
- Adagrasib + Lapatinib Major
Frequently asked questions
Can I take Lapatinib with Zafirlukast?
MediHelp rates the interaction as moderate. Lapatinib 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. Lapatinib is a CYP3A4 substrate, and zafirlukast may modestly increase its exposure. Higher lapatinib levels could increase diarrhea, rash, hepatotoxicity and QT prolongation.
How serious is the interaction between Lapatinib 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 liver function and watch for diarrhea and QT-related symptoms, with an ECG if risk factors are present. Reduce the lapatinib dose or choose an alternative to zafirlukast if toxicity develops.
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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