Drug Interactions between Biktarvy and Viramune XR

MONITOR: Coadministration with inducers of CYP450 3A4, particularly those that can also induce uridine diphosphate glucuronosyltransferase (UGT) 1A1, may decrease 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 study subjects, administration of a single 75 mg dose of bictegravir during treatment with rifampin 600 mg once daily decreased mean bictegravir peak plasma concentration (Cmax) and systemic exposure (AUC) by 28% and 75%, respectively, compared to administration of bictegravir alone. When bictegravir 75 mg once daily was coadministered with rifabutin 300 mg once daily, mean bictegravir Cmax, AUC and trough plasma concentration (Cmin) decreased by 20%, 38% and 56%, respectively. These results are consistent with the fact that rifampin is a more potent inducer of CYP450 3A4 than rifabutin. Rifampin is also a known inducer of UGT1A1. The interaction has not been studied with other, less potent inducers than rifampin and rifabutin.

MANAGEMENT: The potential for diminished pharmacologic effects of bictegravir should be considered during coadministration with CYP450 3A4 inducers. Alternative treatments may be required if an interaction is suspected.

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