Cytochrome P450 Oxidase Isoenzyme CYP2C19 is an enzyme that plays a significant role in the metabolism of several drugs, including antiplatelet agents such as clopidogrel and anti-ulcer agents such as proton pump inhibitors. CYP2C19 is primarily found in the liver, but it is also present in the small intestine, lungs, and kidneys.
Genetic variations in the CYP2C19 gene can affect the activity of this enzyme, leading to interindividual differences in drug metabolism and therapeutic response. Poor metabolizers (PMs) have reduced CYP2C19 activity due to homozygous or compound heterozygous variants in the gene, while extensive metabolizers (EMs) have normal enzyme activity. Intermediate metabolizers (IMs) have reduced enzyme activity due to heterozygous variants in the gene.
Testing for CYP2C19 genotype can help guide drug therapy and dosing, particularly for drugs with a narrow therapeutic index or drugs that are primarily metabolized by this enzyme. For example, patients who are CYP2C19 PMs may require alternative antiplatelet therapy, while those who are CYP2C19 IMs may require dose adjustment of certain drugs to avoid adverse effects.