Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or P-glycoprotein (P-gp) may increase the plasma concentrations of bosutinib, which is a substrate of the isoenzyme and efflux transporter. In 24 healthy volunteers, administration of a single 100 mg dose of bosutinib with the potent CYP450 3A4 and P-gp inhibitor ketoconazole (400 mg/day for 5 days) under fasting conditions resulted in a 5.2-fold increase in bosutinib peak plasma concentration (Cmax) and 8.6-fold increase in systemic exposure (AUC) compared to administration of bosutinib alone. Ketoconazole also decreased the mean apparent clearance of bosutinib by approximately 9-fold and increased the mean terminal half-life from 46.2 hours to 69.0 hours. No data are available for use with less potent CYP450 3A4 inhibitors or P-gp inhibitors.

MANAGEMENT: Caution is advised when bosutinib is used with CYP450 3A4 or P-gp inhibitors. Patients should be monitored more closely for development of adverse effects such as diarrhea, nausea, vomiting, abdominal pain, myelosuppression, hepatotoxicity, and fluid retention (e.g., pericardial effusion, pleural effusion, pulmonary edema, peripheral edema).

ADJUST DOSING INTERVAL: Food enhances the oral bioavailability of bosutinib. When given with a high-fat meal, bosutinib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 1.8- and 1.7-fold, respectively.

GENERALLY AVOID: Coadministration with grapefruit juice is likely to increase the plasma concentrations of bosutinib, which is primarily metabolized by CYP450 3A4. However, the interaction has not been studied. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit.

MANAGEMENT: Bosutinib should be administered with a meal. The consumption of grapefruit, grapefruit juice, and supplements that contain grapefruit extract should be avoided.