Drug Interaction Report

In vitro studies have shown that high concentrations of clopidogrel inhibit CYP450 2C9 isoenzymes. The metabolism of drugs which are substrates for this enzyme may be decreased, potentiating toxicity of the substrate drug. The clinical significance and magnitude of this interaction is not known. Dose adjustments may be necessary if an interaction is suspected.

ADJUST DOSING INTERVAL: Food may reduce the oral absorption and bioavailability of zafirlukast. In two separate studies, one using a high-fat and the other a high-protein meal, administration of zafirlukast with food reduced the mean bioavailability by approximately 40%.

MANAGEMENT: To ensure maximal oral absorption, zafirlukast should be administered at least 1 hour before or 2 hours after meals.