However, the change in efavirenz concentrations varied by CYP2B6 genotype, such that concomitant anti-TB therapy increased efavirenz concentrations 1.49-fold (95% confidence interval [CI], 1.20 to 2.01) in children with slow metabolizer genotypes but did not affect efavirenz concentrations in extensive or intermediate metabolizers (25). The gene discussed is CYP2B6; the disease is tuberculosis.