Effects of CYP2C19 Genotype on Outcomes of Clopidogrel Treatment

Clopidogrel must be metabolized to an active form to be effective. Cytochrome P-450 variants resulting in slow metabolism may reduce clinical efficacy. This study in patients with acute coronary syndromes or atrial fibrillation did not confirm diminished efficacy in those with slow metabolism. Clopidogrel, when added to aspirin, reduces the rate of major vascular events among patients with acute coronary syndromes and atrial fibrillation. 1 , 2 Recent reports suggest that certain common genetic variants, involving the hepatic cytochrome P-450 system, that are involved in the conversion of clopidogrel to its active metabolite are associated with an increased rate of recurrent cardiovascular events, implying that the benefits of clopidogrel may be attenuated in patients with these genetic variants. Specifically, in patients who are carriers of a loss-of-function CYP2C19 allele (including the *2 and *3 alleles), the conversion of clopidogrel to its active metabolite may be . . .