Drug Interaction Report

GENERALLY AVOID: Coadministration with inducers of CYP450 3A4 isoenzymes may reduce the plasma concentrations of elvitegravir, which is primarily metabolized by the isoenzyme.

MANAGEMENT: Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic antiretroviral drug levels, the manufacturers of elvitegravir single-ingredient and combination products recommend avoiding concomitant use. Alternative treatment combinations that do not include metabolic inducers should be considered whenever possible.

ADJUST DOSING INTERVAL: Food enhances the oral bioavailabilities of both elvitegravir and tenofovir. When a single dose of cobicistat/elvitegravir/emtricitabine/tenofovir (trade name Stribild) was given with a light meal (approximately 373 kcal; 20% fat), mean elvitegravir and tenofovir systemic exposures (AUCs) increased by 34% and 24%, respectively, relative to fasting conditions. When administered with a high-fat meal (approximately 800 kcal; 50% fat), the mean AUC of elvitegravir and tenofovir increased by 87% and 23%, respectively, relative to fasting conditions. The alterations in mean AUCs of cobicistat and emtricitabine were not clinically significant with either the light or high-fat meal.

MANAGEMENT: Cobicistat/elvitegravir/emtricitabine/tenofovir as a fixed-dose preparation should be administered once daily with food. Elvitegravir as a single-ingredient preparation should also be administered once daily with food.