Drug Interaction Report

MONITOR: Coadministration with strong CYP450 3A4 inhibitors may increase plasma concentrations and the risk of adverse effects of clindamycin, which is metabolized predominantly by the isoenzyme.

MANAGEMENT: Caution is advised if clindamycin is used concomitantly with strong CYP450 3A4 inhibitors. The possibility of adverse reactions to clindamycin should be considered during coadministration with strong CYP450 3A4 inhibitors. Dosage adjustments as well as clinical and laboratory monitoring of clindamycin should be considered whenever a strong CYP450 3A4 inhibitor is added to or withdrawn from therapy.

ADJUST DOSING INTERVAL: Food may reduce the systemic bioavailability of amprenavir from fosamprenavir oral suspension. The mechanism of interaction has not been described. According to the product labeling, administration of fosamprenavir oral suspension (1400 mg single dose) with a high-fat meal (967 kcal, 67 g fat, 33 g protein, 58 g carbohydrate) reduced amprenavir peak plasma concentration (Cmax) by 46% and systemic exposure (AUC) by 28% compared to administration in a fasted state. The time to reach peak plasma level (Tmax) was delayed by 0.72 hours. In contrast, the same high-fat meal did not affect the pharmacokinetics of amprenavir from fosamprenavir tablets.

MANAGEMENT: Fosamprenavir suspension should be administered on an empty stomach in adults, but with food in pediatric patients to aid palatability and compliance. If emesis occurs within 30 minutes after dosing the suspension, the dose should be repeated. Fosamprenavir tablets may be taken with or without food.