CYP2B6 is a cytochrome P450 enzyme that metabolizes clinically important drugs including efavirenz, methadone, ketamine, and bupropion 1. The enzyme exhibits monooxygenase activity and is primarily expressed in human liver, with detectable expression in brain, intestine, and kidney 2. CYP2B6 demonstrates substrate-specific catalytic activities, including testosterone hydroxylation and metabolism of cyclophosphamide, with preferential activity toward benzyloxyresorufin and pentoxyresorufin 2. The enzyme also metabolizes environmental toxicants, specifically polychlorinated biphenyls (PCBs), converting them to hydroxylated metabolites in an atropselective manner 3. Additionally, CYP2B6 can bioactivate certain substrates to genotoxic metabolites, as demonstrated with carbamazepine-induced DNA damage at therapeutic concentrations 4. Genetic polymorphisms significantly impact CYP2B6 function, with variants like CYP2B6.6 and CYP2B6.9 showing reduced intrinsic clearance for substrates such as nicotine 5. The enzyme's expression is inducible by phenobarbital and shows high interindividual variability influenced by both genetic factors and non-genetic phenoconverting factors including drug interactions and alcohol consumption 6. CYP2B6 expression levels also correlate with drug response, as seen with phenobarbital treatment efficacy 7.