Drug Interaction Report

GENERALLY AVOID: Coadministration with potent 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 use of ibrutinib in combination with potent CYP450 3A4 inhibitors such as itraconazole, ketoconazole, posaconazole, voriconazole, conivaptan, nefazodone, cobicistat, delavirdine, protease inhibitors, and ketolide and certain macrolide antibiotics should generally be avoided, particularly those that are intended for chronic administration. Some authorities recommend avoiding concomitant use of ibrutinib during and for 2 weeks after treatment with itraconazole. Alternative agents with no or minimal CYP450 3A4 inhibitory potential are recommended whenever possible. If no alternatives exist and the CYP450 3A4 inhibitor is used short-term for 7 days or less, consider interrupting or delaying initiation of ibrutinib treatment until therapy with the inhibitor is complete. Patients should be closely monitored for signs of ibrutinib toxicity such as myelosuppression, bleeding, infection, and renal impairment.

GENERALLY AVOID: Coadministration with grapefruit, grapefruit juice, or Seville oranges may significantly increase the plasma concentrations of ibrutinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Pharmacokinetic modeling suggests that other moderate CYP450 3A4 inhibitors such as diltiazem and erythromycin may increase ibrutinib systemic exposure (AUC) 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.

ADJUST DOSING INTERVAL: Food increases the oral bioavailability of ibrutinib. The mechanism of interaction is unknown. According to the product labeling, administration with food increases ibrutinib exposure approximately 2-fold compared to administration after overnight fasting.

MANAGEMENT: Patients treated with ibrutinib should avoid consumption of Seville oranges, grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Ibrutinib should be taken once daily at approximately the same time each day.

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.