Platelet Function During Extended Prasugrel and Clopidogrel Therapy for Patients With ACS Treated Without Revascularization

ContextThe relationship of platelet function testing measurements with outcomes in patients with acute coronary syndromes (ACS) initially managed medically without revascularization is unknown.ObjectiveTo characterize the differences and evaluate clinical outcomes associated with platelet reactivity among patients with ACS treated with clopidogrel or prasugrel.Design, Setting, and PatientsPatients with medically managed unstable angina or non–ST-segment elevation myocardial infarction were enrolled in the TRILOGY ACS trial (2008 to 2011) comparing clopidogrel vs prasugrel. Of 9326 participants, 27.5% were included in a platelet function substudy: 1286 treated with prasugrel and 1278 treated with clopidogrel.InterventionsAspirin with either prasugrel (10 or 5 mg/d) or clopidogrel (75 mg/d); those 75 years or older and younger than 75 years but who weighed less than 60 kg received a 5-mg prasugrel maintenance dose.Main Outcome MeasuresPlatelet reactivity, measured in P2Y12 reaction units (PRUs), was performed at baseline, at 2 hours, and at 1, 3, 6, 12, 18, 24, and 30 months after randomization. The primary efficacy end point was a composite of cardiovascular death, myocardial infarction, or stroke through 30 months.ResultsAmong participants younger than 75 years and weighing 60 kg or more, the median PRU values at 30 days were 64 (interquartile range IQR, 33-128) in the prasugrel group vs 200 (IQR, 141-260) in the clopidogrel group (P ConclusionsAmong patients with ACS without ST-segment elevation and initially managed without revascularization, prasugrel was associated with lower platelet reactivity than clopidogrel, irrespective of age, weight, and dose. Among those in the platelet substudy, no significant differences existed between prasugrel vs clopidogrel in the occurence of the primary efficacy end point through 30 months and no significant association existed between platelet reactivity and occurrence of ischemic outcomes.Trial Registrationclinicaltrials.gov Identifier: NCT00699998