Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or uridine diphosphate glucuronosyltransferase (UGT) 1A1 may increase the plasma concentrations of bictegravir. According to the product labeling, bictegravir is a substrate of both CYP450 3A4 and UGT1A1; however, the extent to which each enzymatic pathway contributes to the metabolic clearance of bictegravir has not been reported. In healthy volunteers studied under fasted conditions, administration of a single 75 mg dose of bictegravir during treatment with the potent CYP450 3A4 inhibitor voriconazole (300 mg twice daily) increased mean bictegravir peak plasma concentration (Cmax) and systemic exposure (AUC) by 9% and 61%, respectively, compared to administration of bictegravir alone. In addition, in healthy volunteers studied under fed conditions, administration of a single 75 mg dose of bictegravir during treatment with the potent CYP450 3A4 and UGT1A1 inhibitor atazanavir (400 mg once daily) increased mean bictegravir AUC by 315%, compared to administration of bictegravir alone.

MANAGEMENT: Caution is advised when bictegravir is used with CYP450 3A4 and UGT1A1 inhibitors. Patients should be monitored for increased adverse effects such as diarrhea, nausea, and vomiting.

GENERALLY AVOID: Taking stiripentol on an empty stomach may reduce its oral bioavailability. Stiripentol degrades rapidly when exposed to gastric acid in an empty stomach.

GENERALLY AVOID: Alcohol may potentiate the depressant effects of stiripentol on the central nervous system. Concomitant use may result in increased sedation and dizziness as well as impairment of psychomotor skills.

GENERALLY AVOID: It is not known whether stiripentol may reduce theophylline and caffeine metabolism, as data on the potential for inhibition of CYP450 1A2 are limited. Consumption of foods and nutritional products such as cola drinks (which contain significant quantities of caffeine) and chocolate (which contains caffeine and trace amounts of theophylline) may be unsafe during treatment with stiripentol, particularly in children.

MANAGEMENT: Stiripentol should be taken during a meal for optimal absorption; however, it should not be taken with milk, dairy products (e.g., yogurt, soft cream cheese), fruit juice, or carbonated beverages. Patients should be advised to avoid or limit consumption of alcohol and to avoid activities requiring mental alertness such as driving or operating hazardous machinery until they know how the medication affects them. Food and beverages that may contain caffeine or theophylline such as colas, chocolate, coffee, tea, or energy drinks should also be avoided during treatment with stiripentol.

Food enhances the oral absorption and bioavailability of tenofovir, the active entity of tenofovir disoproxil fumarate. According to the product labeling, administration of the drug following a high-fat meal increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of tenofovir by approximately 14% and 40%, respectively, compared to administration in the fasting state. However, administration with a light meal did not significantly affect the pharmacokinetics of tenofovir compared to administration in the fasting state. Food delays the time to reach tenofovir Cmax by approximately 1 hour. Tenofovir disoproxil fumarate may be administered without regard to meals.