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, Acetylsalicylic Acid. 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 + Acetylsalicylic Acid— 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.