Drug Interactions between aprepitant and ibrutinib

ADJUST DOSE: Coadministration with moderate inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of ibrutinib, which is primarily metabolized by the isoenzyme. In 18 healthy volunteers administered a single 120 mg dose of ibrutinib alone on day 1 and a single 40 mg dose of ibrutinib on day 7 in combination with ketoconazole 400 mg daily on days 4 thru 9, there was a 29-fold increase in dose-normalized ibrutinib peak plasma concentration (Cmax) and 24-fold increase in dose-normalized systemic exposure (AUC) during treatment with ketoconazole compared to administration alone. Pharmacokinetic modeling suggests that moderate CYP450 3A4 inhibitors such as diltiazem and erythromycin may increase the AUC of ibrutinib by 6- to 9-fold under fasting condition. The safety and efficacy of these exposures are unknown. The highest ibrutinib dose evaluated in clinical trials was 12.5 mg/kg (actual doses of 840 to 1400 mg) given for 28 days, which yielded single dose AUC values that were approximately 50% greater than steady-state exposures seen at the highest indicated dose of 560 mg.

MANAGEMENT: The dosage of ibrutinib should be adjusted according to the indication in the product labeling whenever it is used in combination with a moderate CYP450 3A4 inhibitor such as amprenavir, aprepitant, atazanavir, ciprofloxacin, crizotinib, darunavir, diltiazem, dronedarone, erythromycin, fluconazole, fosamprenavir, fosaprepitant, imatinib, or verapamil. All patients should be closely monitored for signs of ibrutinib toxicity such as myelosuppression, bleeding, infection, and renal impairment.