CYP2B6 and tuberculosis: HIV-infected patients with or without TB who had received combination antiretroviral therapy containing efavirenz (600 mg daily) for two weeks or greater were enrolled for determinations of CYP2B6 G516T polymorphism and plasma efavirenz concentrations with the use of polymerase-chain-reaction restriction fragment-length polymorphism and high-performance liquid chromatography, respectively.