Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 2C8 may increase the plasma concentrations of tucatinib, which is primarily metabolized by the isoenzyme. When gemfibrozil (600 mg twice daily), a potent CYP450 2C8 inhibitor, was administered with a single tucatinib dose of 300 mg, tucatinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 1.6-fold and 3-fold, respectively.

MANAGEMENT: Increased monitoring is advised if tucatinib is coadministered with CYP450 2C8 inhibitors. Dosage adjustments may be required based on clinical response and tolerance.

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.