Clinical and Pharmacological Parameters Determine Relapse During Clopidogrel Treatment of Acute Coronary Syndrome

The therapeutic efficacy of clopidogrel as an antiplatelet drug varies among individuals, being the mainstream hypothesis that its bioavailability depends on the individual genetic background and/or interactions with other drugs. A total of 477 patients receiving double antiaggregation therapy with aspirin and clopidogrel, after suffering a first event, were followed for 1 year to record relapse, as a surrogate end point to measure their therapeutic response, as defined by presenting with an acute coronary event (unstable angina, ST-segment-elevation myocardial infarction, or non-ST-segment-elevation myocardial infarction), stent thrombosis/restenosis, or cardiac mortality. Anthropometric, clinical, and pharmacological variables along with CYP2C19 genotypes were analyzed for their association with the disease relapse phenotype. Only 75 patients (15%) suffered a relapse, which occurred during the first 6 months of therapy, with a peak at 4.5 months. An initial univariate analysis identified that patients in the relapse group were significantly older (67.4 ± 11.0 vs 61.6 ± 12.3 years old) and presented with diffuse coronary disease, insulin-dependent type 2 diabetes mellitus dyslipidemia, and arterial hypertension. A poor clinical response to the platelet antiaggregation regime also occurred more frequently among patients taking acenocoumarol and calcium channel blockers, along with aspirin and clopidogrel, while no association was found according to CYP2C19 genotypes. A retrospective multivariate analysis indicated that patients belonging to the nonresponder phenotype to treatment with aspirin and clopidogrel were older, presented with diffuse coronary disease, a group largely overlapping with type 2 insulin-dependent diabetes mellitus, and were taking dihidropyrimidinic calcium channel blockers.