TY - JOUR T1 - Carrying one or two reduced-function <em>CYP2C19</em> alleles is associated with an increased risk of major adverse cardiovascular events in people undergoing percutaneous coronary intervention and treated with clopidogrel JF - Evidence Based Medicine JO - Evid Based Med SP - 124 LP - 125 DO - 10.1136/ebm1203 VL - 16 IS - 4 AU - Andrea H Ramirez AU - Jessica T Delaney AU - Alan R Shuldiner Y1 - 2011/08/01 UR - http://ebm.bmj.com/content/16/4/124.abstract N2 - Commentary on: Mega JL, Simon T, Collet JP, et al. Reduced-function CYP2C19 genotype and risk of adverse clinical outcomes among patients treated with clopidogrel predominantly for PCI: a meta-analysis. JAMA 2010;304:1821–30.OpenUrlCrossRefPubMedWeb of Science The antiplatelet effect of clopidogrel varies among users as measured by ex vivo platelet function studies and clinical outcomes. Studies have identified common reduced-function variants in the cytochrome P450 enzyme gene, CYP2C19, that are associated with clopidogrel responsiveness. The fully functional form of the gene, designated CYP2C19*1, metabolises clopidogrel from its native prodrug state to its active antiplatelet metabolite more efficiently than CYP2C19*2, found commonly in Caucasians, African Americans and Asians, and CYP2C9*3, common only in Asians. Individuals carrying one of these reduced-function alleles are intermediate metabolisers, whereas those carrying two reduced-function alleles are poor metabolisers. In patients on clopidogrel, these variants have been associated with poorer clinical outcomes in many studies, although not all have shown an effect, particularly in patients with one reduced-function allele. Relevant studies for this meta-analysis were gathered with a combination of computer database searches and expert consultation. Of the 31 possible studies, 9 met the inclusion criteria of patients predominantly invasively managed with percutaneous coronary intervention (PCI) and with … ER -