Drug Interactions between entecavir and ganciclovir

ADJUST DOSING INTERVAL: Food delays but enhances the oral absorption and bioavailability of ganciclovir capsules, possibly due to prolongation of gastrointestinal transit time. In 20 HIV- and CMV-seropositive subjects, ganciclovir dosing (1000 mg every 8 hours) following a standardized high-fat breakfast increased the mean steady-state peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of ganciclovir by an average of 15% and 22%, respectively, compared to dosing after an overnight fast. The time to reach peak plasma concentration (Tmax) was prolonged from 1.8 to 3 hours. In another study of 15 such patients, administration of ganciclovir (2000 mg) within 30 minutes following a high-fat breakfast increased the Cmax and AUC an average of 111% and 114%, respectively, compared to administration in the fasting state (i.e. at least 1 hour before or 2 hours after a meal or snack). Over the total day of dosing (2000 mg orally three times a day), there was a mean increase of 48% and 97% in Cmax and AUC, respectively, and a 36% decrease in half-life during administration with meals.

MANAGEMENT: To ensure maximal oral absorption, oral ganciclovir should be administered with or immediately after a meal.

ADJUST DOSING INTERVAL: Food delays the oral absorption and reduces the oral bioavailability of entecavir. According to the product labeling, administration of entecavir 0.5 mg with a standard high-fat meal or a light meal resulted in a delay in absorption by 0.25 to 0.75 hours, a decrease in the peak plasma concentration (Cmax) by 44% to 46%, and a decrease in the area under the plasma concentration-time curve (AUC) by 18% to 20% compared to administration in the fasting state.

MANAGEMENT: To ensure maximal oral absorption, entecavir should be administered on an empty stomach at least 2 hours after a meal and 2 hours before the next meal.