Cytochrome P450 family 2 subfamily D member 6 and Cytochrome P450 family 3 subfamily A member 4 (CYP2D6 and CYP3A4)

Cytochrome P450 2D6 (CYP2D6) and Cytochrome P450 3A4 (CYP3A4) are the two most critical enzymes in the human cytochrome P450 superfamily, collectively responsible for the Phase I metabolism of approximately 70-80% of all clinically used drugs [1, 16]. CYP3A4 is the most abundant P450 enzyme in the liver and small intestine, where it metabolizes about 50% of marketed drugs, including large lipophilic molecules, steroids, and immunosuppressants [6, 8, 16]. CYP2D6, while less abundant, is highly polymorphic and processes roughly 25% of drugs, such as antidepressants, antipsychotics, beta-blockers, and opioids [4, 9, 17]. These enzymes are essential for drug detoxification and the bioactivation of prodrugs like codeine and tamoxifen [11, 17]. Genetic variations in CYP2D6 lead to distinct metabolizer phenotypes—ranging from poor to ultra-rapid—which significantly impact drug efficacy and safety [4, 12]. Furthermore, both enzymes are frequent sites of drug-drug interactions, where inhibition or induction by one agent can lead to toxic accumulations or sub-therapeutic levels of co-administered medications [3, 15, 16].

Other names

CYP2D6CYP3A4Debrisoquine 4-hydroxylaseNifedipine oxidaseP450-DB1P450-PCN1CYP3A3Cytochrome P450 2D6Cytochrome P450 3A4

Phase I oxidative metabolism, including hydroxylation, N-dealkylation, O-dealkylation, and epoxidation of xenobiotics and endogenous compounds.