Double-blind, randomized, prospective comparison of loading doses of 600 mg clopidogrel versus 60 mg prasugrel in patients with acute ST-segment elevation myocardial infarction scheduled for primary percutaneous intervention: the ETAMI trial (early thienopyridine treatment to improve primary PCI in patients with acute myocardial infarction).

Objectives: This study compared the timing of onset of antiplatelet action after treatment with clopidogrel and prasugrel at first medical contact in patients with ST-segment elevation myocardial infarction (STEMI) scheduled for primary percutaneous coronary intervention (PPCI).

Background: Little is known about the timing of onset of antiplatelet action after a pre-percutaneous coronary intervention (PCI) loading dose of clopidogrel or prasugrel in patients with STEMI.

Methods: This double-blind, prospective study randomized 62 patients with STEMI scheduled for PPCI in the ambulance or the emergency department to 60 mg prasugrel (n = 31) or 600 mg clopidogrel (n = 31). The primary endpoint was the platelet reactivity index (PRI) measured with the vasodilator-stimulated phosphoprotein assay 2 h after intake of the study medication. Secondary endpoints were PRI after 4 h, TIMI (Thrombolysis In Myocardial Infarction) patency of the infarct-related artery before and after PCI, and clinical events until day 30.

Results: The PRI after 2 h (50.4 ± 32.7% vs. 66.3 ± 22.2%; p = 0.035) and after 4 h (39.1 ± 27.5% vs. 54.5 ± 49.3%; p = 0.038) were significantly lower with prasugrel compared with clopidogrel. In addition, the rate of patients with a PRI <50% tended to be higher with prasugrel compared with clopidogrel after 2 h (46.7% vs. 28.6%; p = 0.15) and after 4 h (63.0% vs. 38.9%; p = 0.06). There were no significant differences in TIMI 2/3 patency before PCI (39.2% vs. 31.0%; p = 0.43) and TIMI 3 patency after PCI (88.5% vs. 89.3%; p = 0.92).

Conclusions: The pre-PCI administration of prasugrel in patients with STEMI undergoing PPCI was associated with a significant faster platelet inhibition compared with clopidogrel. Therefore, prasugrel should be preferred to clopidogrel in this setting. (ETAMI-Study: Early Thienopyridine Treatment to Improve Primary PCI in Patients With Acute Myocardial Infarction; NCT01327534).