Objectives A more rapid onset of antiplatelet effect following loading with prasugrel and ticagrelor compared to clopidogrel was demonstrated for healthy subjects and patients with stable coronary artery disease. These results have endorsed the clinical practice of delaying administration of P2Y12 antagonists until completion of angiography even in patients presenting with acute coronary syndrome (ACS). However, pharmacodynamic data supporting this procedure in patients with ACS are lacking.

Methods This prospective registry enrolled 119 patients admitted with STEMI/NSTEMI and scheduled for percutaneous coronary intervention (PCI). All patients received a bolus dose of acetylsalicylic acid and a loading dose (LD) of either prasugrel (P: 60 mg) or ticagrelor (T: 180 mg) before PCI. Treatment with prasugrel/ticagrelor was at the discretion of the attending physician. Platelet reactivity was assessed by VerifyNow PRU test at PCI and at day1 following intervention 2 to 4 hours after administration of the first maintenance dose of prasugrel 10 mg/ticagrelor 90 mg.

Results Our registry comprised 40 patients with STEMI (P: 21 and T: 19) and 79 patients with NSTEMI (P: 28 and T: 51). Antiplatelet effects assessed by VerifyNow PRU test are summarised in the table. At PCI, high on-treatment platelet reactivity (HTPR: >208 PRU) was determined frequently irrespective of the used P2Y12 ADP antagonist (P: 35%, T: 29%; p = 0.548). At day 1 after PCI, platelet reactivity was significantly lower in patients on prasugrel than in patients on ticagrelor. Only two patients displayed HTPR at day 1 after PCI.

Conclusions Onset of antiplatelet effect of prasugrel and ticagrelor is delayed in STEMI/NSTEMI patients leading to a large proportion of patients with high on-treatment platelet reactivity during PCI when performed timely.