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.

GENERALLY AVOID: Grapefruit and/or grapefruit juice may increase the systemic exposure to palbociclib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Increased exposure to palbociclib may increase the risk of adverse effects such as infections, neutropenia, leukopenia, anemia, thrombocytopenia, anorexia, nausea, vomiting, diarrhea, stomatitis, alopecia, asthenia, peripheral neuropathy, and epistaxis.

ADJUST DOSING INTERVAL: Food may enhance the oral bioavailability of palbociclib capsules and reduce the intersubject variability of palbociclib exposure. According to the product labeling, absorption and exposure of palbociclib from its oral capsule formulation were very low in approximately 13% of the population when taken in the fasted state. Food intake increased the palbociclib exposure in this small subset of the population but did not alter exposure in the rest of the population to a clinically relevant extent. Compared to palbociclib capsules given under overnight fasted conditions, the population average palbociclib peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 38% and 21%, respectively, when given with high-fat, high-calorie food (approximately 800 to 1000 calories; 150, 250, and 500 to 600 calories from protein, carbohydrate and fat, respectively); by 27% and 12%, respectively, when given with low-fat, low-calorie food (approximately 400 to 500 calories; 120, 250, and 28 to 35 calories from protein, carbohydrate and fat, respectively); and by 24% and 13%, respectively, when given with moderate-fat, standard calorie food (approximately 500 to 700 calories; 75 to 105, 250 to 350 and 175 to 245 calories from protein, carbohydrate and fat, respectively) one hour before and two hours after palbociclib capsule dosing.

MANAGEMENT: Patients should avoid consumption of grapefruit or grapefruit juice while on treatment with palbociclib. To avoid variability in drug absorption between doses, palbociclib capsules should be taken with food. Palbociclib tablet formulations may be taken with or without food.