Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 2C9 may increase the plasma concentrations of torsemide. The interaction has not been evaluated in pharmacokinetic studies; however, torsemide has been shown to undergo metabolism by CYP450 2C9.

MANAGEMENT: Caution is advised when torsemide is prescribed with CYP450 2C9 inhibitors. Patients should be monitored for potentially increased adverse effects such as dehydration, hypotension, electrolyte imbalances, hyperglycemia, tinnitus, and hearing loss.

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.