Zafirlukast has 11 known drug interactions based on U.S. FDA drug labeling data. 2 are classified as major interactions requiring close medical supervision. Notable interactions include combinations with Warfarin, Warfarin Sodium, Aspirin. Patients taking Zafirlukast should inform their healthcare provider of all current medications — including over-the-counter drugs and supplements — to avoid potentially harmful combinations. Data sourced from OpenFDA and the NIH National Library of Medicine.
- Total
- 11
- Major
- 2
- Moderate
- 8
- Minor
- 1
Major (2)
- Zafirlukast + Warfarin— CYP2C9 inhibitor that increases warfarin effect and INR; requires close INR monitoring
- Zafirlukast + Warfarin Sodium— CYP2C9 inhibitor that increases warfarin effect and INR; requires closer INR monitoring.
Moderate (8)
- Zafirlukast + Aspirin— Aspirin increases zafirlukast mean plasma levels by approximately 45%.
- Zafirlukast + Carbamazepine— Zafirlukast may interact with carbamazepine as it is metabolized by CYP2C9. Care should be exercised when coadministered…
- Zafirlukast + Erythromycin— Erythromycin decreases zafirlukast plasma levels by approximately 40% due to decreased zafirlukast bioavailability.
- Zafirlukast + Fluconazole— Coadministration of zafirlukast with fluconazole, a moderate CYP2C9 inhibitor, resulted in increased plasma levels of za…
- Zafirlukast + Itraconazole— Itraconazole is a strong CYP2C9 inhibitor likely to increase zafirlukast exposure.
- Zafirlukast + Phenytoin— Zafirlukast may interact with phenytoin as it is metabolized by CYP2C9. Care should be exercised when coadministered.
- Zafirlukast + Theophylline— Rare cases of increased theophylline levels and toxicity reported with zafirlukast addition. Zafirlukast levels decrease…
- Zafirlukast + Tolbutamide— Zafirlukast may interact with tolbutamide as it is metabolized by CYP2C9. Care should be exercised when coadministered.
Minor (1)
- Zafirlukast + Ethinyl Estradiol— Zafirlukast has no significant effect on ethinyl estradiol plasma concentrations or contraceptive efficacy.