Combined Effect of CYP2B6 and NAT2 Genotype on Plasma Efavirenz Exposure During Rifampin-based Antituberculosis Therapy in the STRIDE Study

In STRIDE, slow metabolizer CYP2B6 and NAT2 genotypes were each associated with increased plasma efavirenz concentrations during antituberculosis therapy. Concentrations were greater on therapy than off therapy in 58% with CYP2B6 and 93% with NAT2 slow metabolizer genotypes. Individuals with slow metabolizer genotypes in both genes had markedly elevated concentrations.