Drug Interaction Report

ADJUST DOSE: Coadministration with moderate inducers of CYP450 2C9 or 3A4 may decrease the plasma concentrations and therapeutic effects of erdafitinib. The mechanism is induction of CYP450 2C9- or 3A4-mediated metabolism of erdafitinib, which has been shown to be metabolized by these isoenzymes.

MANAGEMENT: According to the manufacturer, if a moderate CYP450 2C9 or 3A4 inducer is coadministered at the start of erdafitinib therapy, the recommended dose of erdafitinib should be administered. If a moderate CYP450 2C9 or 3A4 inducer is coadministered after the initial dose increase period, the dose of erdafitinib may be increased up to 9 mg once daily based on serum phosphate levels and tolerability. When a moderate CYP450 2C9 or 3A4 inducer is discontinued, the current dose of erdafitinib may be continued in the absence of erdafitinib toxicity.

ADJUST DOSING INTERVAL: Coadministration with food increases the oral bioavailability of etravirine. The mechanism is unknown. Compared to administration following a meal, the systemic exposure (AUC) to etravirine was decreased by about 50% when the drug was administered under fasting conditions. The types of meal studied (ranging from 345 kilocalories containing 17 grams fat to 1160 kilocalories containing 70 grams fat) did not appear to make a difference with respect to impact on etravirine bioavailability.

MANAGEMENT: Etravirine should always be administered following a meal.