Drug Interaction Report

MONITOR: Coadministration with inducers of CYP450 isoenzymes may decrease the plasma concentrations of etravirine, which is a substrate of CYP450 2C19, 2C9, and 3A4.

MANAGEMENT: Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic antiretroviral drug levels, caution is advised if etravirine is used with CYP450 inducers. Close clinical and laboratory monitoring of antiretroviral response is recommended.

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.