Temporal Changes in Platelet Response in Acute Coronary Syndrome Patients With Prasugrel and Clopidogrel After Stent Implantation.

Background: Prasugrel has been shown to provide more potency and less variability than clopidogrel, but its potential temporal variability has not been described. Methods and Results: We conducted a prospective open-label study, evaluating platelet reactivity overtime in acute coronary syndrome (ACS) patients on aspirin and clopidogrel (n=60) or prasugrel (n=61), after a percutaneous coronary intervention (PCI). Blood samples were taken at discharge and at 3 and 6 months. Platelet function tests included VerifyNow (VN-P2Y12), and Multiplate Aggregometry (MEA). By means of VN-P2Y12, prasugrel patients displayed significantly (P<0.001) higher platelet inhibition than clopidogrel patients over time, although there were not significant differences using MEA. Prasugrel patients showed higher platelet inhibition at baseline than at 3 months (59.3 +/- 8.1 vs. 105.0 +/- 49.2; P<0.001), without significant change at 6 months (107.9 +/- 72.0; P=0.919 vs. 3 months). Clopidogrel patients showed a similar trend (160.1 +/- 65.1, 184.8 +/- 62.7 and 185.0 +/- 53.3; baseline vs. 3 months P=0.060; 3 months vs. 6 months P=0.974). High platelet reactivity (HPR) was shown in 16.3% prasugrel patients, with no patient consistently remaining in HPR over time. HPR was detected in 36.6% of the clopidogrel patients, being consistently observed in 15.0% of them. Low platelet reactivity (LPR) was detected in 60.5% prasugrel and 9.8% clopidogrel patients. Conclusions: Prasugrel patients showed less temporal variation than patients on clopidogrel in terms of HPR. In contrast, higher variability in LPR was detected in prasugrel patients for up to 6 months' follow-up.