Drug Interaction Report

GENERALLY AVOID: Coadministration of pexidartinib with strong CYP450 3A4 inhibitors and/or uridine diphosphate glucuronosyltransferase (UGT) inhibitors may significantly increase the plasma concentrations and the incidence and severity of adverse effects of pexidartinib, including potentially fatal hepatotoxicity. The proposed mechanism is inhibition of CYP450 3A4 and/or UGT, the primary isoenzymes responsible for the metabolic clearance of pexidartinib. Concomitant administration of itraconazole, a strong CYP450 3A4 inhibitor, increased pexidartinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 48% and 70%, respectively. Coadministration with probenecid, a UGT inhibitor, increased pexidartinib Cmax and AUC by 5% and 60%, respectively.

MANAGEMENT: The use of pexidartinib with strong CYP450 3A4 inhibitors and/or UGT inhibitors should generally be avoided. If concomitant use is required, the dose of pexidartinib should be reduced according to the manufacturer's recommendations. If concomitant use of a strong CYP450 3A4 inhibitor or UGT inhibitor is discontinued, the dose of pexidartinib may be increased, after 3 plasma half-lives of the strong CYP450 3A4 inhibitor or UGT inhibitor, to the dose that was used prior to starting the strong CYP450 3A4 inhibitor or UGT inhibitor.

ADJUST DOSING INTERVAL: The presence of food may increase the absorption and toxicity of pexidartinib. Administration of pexidartinib with a high-fat meal increased peak plasma concentration (Cmax) and systemic exposure (AUC) by 100% and prolonged the time to reach peak plasma concentration (Tmax) by 2.5 hours.

GENERALLY AVOID: Grapefruit or grapefruit juice may increase the plasma concentration and risk of adverse effects of pexidartinib, including potentially fatal hepatotoxicity. The mechanism is inhibition of CYP450 3A4-mediated metabolism of pexidartinib by certain compounds present in grapefruits. Concomitant administration of itraconazole, a strong CYP450 3A4 inhibitor, increased pexidartinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 48% and 70%, respectively.

MANAGEMENT: Pexidartinib should be administered on an empty stomach, at least one hour before or two hours after a meal or snack. Consumption of grapefruit or grapefruit juice should generally be avoided during pexidartinib therapy. If concomitant use is unavoidable, the dose of pexidartinib should be reduced according to the manufacturer's recommendations. If concomitant use of grapefruit or grapefruit juice is discontinued, the dose of pexidartinib may be increased (after 3 plasma half-lives of a strong CYP450 3A4 inhibitor) to the dose that was used prior to consumption of grapefruit or grapefruit juice.

ADJUST DOSING INTERVAL: Food may reduce the oral absorption and bioavailability of sorafenib. According to the product labeling, sorafenib bioavailability was reduced by 29% when administered with a high-fat meal compared to administration in the fasted state. When given with a moderate-fat meal, bioavailability was similar to that in the fasted state.

MANAGEMENT: To ensure maximal and consistent oral absorption, sorafenib should be taken at least one hour before or two hours after eating.

The recommended maximum number of medicines in the 'multikinase inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'multikinase inhibitors' category:

• Nexavar (sorafenib)
• pexidartinib

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.