Effects of rifampin-based antituberculosis therapy on plasma efavirenz concentrations in children vary by CYP2B6 genotype

Antituberculosis treatment was not associated with reduced efavirenz concentrations in children, which does not support increased efavirenz doses. Children with slow metabolizer genotype have increased efavirenz concentrations during antituberculosis treatment, likely due to isoniazid inhibiting enzymes involved in accessory metabolic pathways for efavirenz.