Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of axitinib, which is primarily metabolized by the isoenzyme. In 32 healthy volunteers, administration of a single 5 mg dose of axitinib on day 4 of treatment with the potent CYP450 3A4 inhibitor ketoconazole (400 mg/day for 7 days) resulted in a 1.5-fold increase in mean axitinib peak plasma concentration (Cmax) and 2-fold increase in mean systemic exposure (AUC) compared to administration of axitinib alone. The mean plasma half-life of axitinib also increased from 9.4 hours when given alone to 13.1 hours in the presence of ketoconazole. The combination was well tolerated by study subjects. Most treatment-related adverse events were mild in severity, with headache and nausea reported most frequently. No clinically significant effects on blood pressure were observed for single-dose axitinib plus ketoconazole relative to axitinib alone.

MANAGEMENT: Caution is advised if axitinib is prescribed with CYP450 3A4 inhibitors. Alternative agents with no or minimal CYP450 3A4 inhibition potential are recommended whenever possible. Otherwise, patients should be monitored closely for development of toxicity such as hypertension/hypertensive crisis, arterial and venous thromboembolic complications, hemorrhage, gastrointestinal perforation or fistula, thyroid dysfunction, reversible posterior leukoencephalopathy syndrome, proteinuria, and liver enzyme elevations or hepatic impairment.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of axitinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit.

MANAGEMENT: Patients treated with axitinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Axitinib may be administered with or without food.