RESUMO
BACKGROUND: Clopidogrel is a pro-drug and its intestinal absorption is limited by the P-glycoprotein encoded by the ABCB1 gene. It is metabolized hepatically by cytochrome P450 enzymes encoded by CYP genes to produce an active metabolite that antagonizes the P2Y12 platelet receptor. Some patients exhibit poor clopidogrel responsiveness due to polymorphisms, resulting in thrombotic events. The aim of this study was to determine the relationship between poor clopidogrel responsiveness and the ABCB1, CYP and P2RY12 gene polymorphisms among patients undergoing percutaneous coronary intervention (PCI). METHODS AND RESULTS: Two hundred seventy-six patients who underwent PCI were included in this study. Clopidogrel responsiveness was determined via optical aggregometry in platelet-rich plasma using 10 µM ADP. Patients exhibiting a platelet aggregation response higher than 70% were classified as poor responders. The genetic polymorphisms were analyzed via real-time PCR. Poor responsiveness to clopidogrel was noted in 22.1% of the patients. The TT genotype of the C3435T polymorphism of the ABCB1 gene and omeprazole usage were each associated with poor clopidogrel responsiveness (Exp (ß) 2.73, p=0.009 and Exp (ß) 3.86, p=0.04, respectively). CONCLUSION: Poor clopidogrel responsiveness is associated with the TT genotype of the C3435T polymorphism of the ABCB1 gene.