Clopidogrel Resistance

Platelet activation and aggregation play important roles in ischemic event occurrences in high-risk patients with coronary artery disease (CAD). Dual antiplatelet therapy with aspirin and a P2Y12 receptor inhibitor is a key strategy to prevent major adverse cardiovascular events in CAD patients undergoing percutaneous coronary intervention (PCI) or those with acute coronary syndrome (ACS). Interindividual variability in response to aspirin and clopidogrel administration along with the influence of different polymorphisms on platelet reactivity has been demonstrated in healthy subjects or CAD patients. Reduced pharmacodynamic effect and reduced clinical efficacy of clopidogrel have been well documented in PCI or ACS patients carrying a loss-of-function allele of the CYP2C19 gene. In addition, accumulating data from numerous clinical studies underscore the importance of "high on-treatment platelet reactivity (HPR)" as a prognostic risk factor. However, the influence of HPR and/or genotype on clinical outcomes must be assessed in the context of the overall disease risk level (ACS vs. non-ACS, diabetes vs. non-diabetes, and old age), post-PCI time (early vs. late) and ethnicity. (Korean J Med 2013;85:1-9).