CYP2B6 and tuberculosis: Biochemical variables, efavirenz pharmacokinetics as well as pharmacogenetic variations in six candidate genes relevant for metabolism and transport of ARV and anti-TB drugs; namely; CYP2B6, CYP3A5, UGT2B7, NAT2, ABCB1 and SLCO1B1 (OATP1B1) were investigated.