Cytochromes are proteins that catalyze electron transfer reactions of well-known metabolic pathways and are classified in various superfamilies. The CYP, or P450, superfamily accounts for 90% of the oxidative metabolism of clinical drugs. One member of this superfamily, P450 2D6 (or CYP2D6), singlehandedly metabolizes about 25% of all medications in the human liver. Cytochrome P450 2D6: Structure, Function, Regulation, and Polymorphism reviews the current knowledge of CYP2D6 as well as the maturing body of evidence indicating its significance to clinical and pharmacological...