CYP2C9 and CYP3A4

CYP2C9 and CYP3A4 are highly expressed enzymes of the cytochrome P450 family found predominantly in the liver. Each enzyme catalyzes the oxidation of xenobiotics and endogenous compounds, playing an essential role in phase I drug metabolism. CYP2C9 metabolizes about 15% of all prescription drugs, including several with a narrow therapeutic index. CYP3A4, the most abundant CYP in human liver, participates in the metabolism of over 50% of clinically used drugs. Both enzymes exhibit genetic polymorphisms that significantly impact individual drug responses, efficacy, and risk of adverse reactions. Clinical genotyping and drug monitoring are essential for drugs highly dependent on these enzymes for clearance. Both are major targets in drug development and in clinical risk management for drug interactions and precision medicine.

Other names

Cytochrome P450 2C9Cytochrome P450 3A4P450 enzymesCYP2C9 enzymeP450 2C9CYP3A4 enzymeP450 3A4

Drugs targeting these enzymes may act as inhibitors (reduce enzyme activity; e.g., amiodarone, metronidazole, miconazole for CYP2C9; ketoconazole, grapefruit juice for CYP3A4). Inducers (increase enzyme activity; e.g., rifampin, barbiturates, carbamazepine for both). Substrates (drugs metabolized by these enzymes). Genetic variants alter enzyme function, changing drug metabolism rate.