Is platelet inhibition correlated with time from last intake on P2Y12 blockers after an acute coronary syndrome? A pilot study

Delay from the last intake of drug could be an important and unexplored variable in the biological response to antiplatelet agents after acute coronary syndrome (ACS) discharge. The objective was to define the impact of the delay from P2Y12 blocker intake on the platelet inhibition level. We compared ticagrelor-, prasugrel-, and clopidogrel-treated patients. All consecutive patients, who had been addressed between 2013 and 2014 for ACS, treated with aspirin and a P2Y12 blocker as maintenance dose, were eligible. One month after discharge, blood sample and a questionnaire were proposed to the patient by a nurse blinded to the protocol. On this questionnaire, three questions about name of the drug, regularity of the intakes, and hour of the last intake were collected. The response to antiplatelet therapy was assessed using platelet reactivity index vasodilator-stimulated phosphoprotein (PRI VASP) and % of adenosine-5'-diphosphate-induced aggregation (% ADP). The primary objective of this study was to evaluate the correlation between platelet inhibition and delay from drug intake. We enrolled 474 ACS treated with clopidogrel 75 mg in 182 cases (38% patients), prasugrel in 190 cases (40%), or ticagrelor in 102 patients (22%). We observed a significant correlation between delay from intake and PRI VASP and % ADP for ticagrelor (r = 0.25, p = 0.01; r = 0.21, p = 0.03; respectively). On clopidogrel (r = 0.09, p = 0.24; r = 0.02, p = 0.80; respectively) and prasugrel (r = 0.02, p = 0.82; r = 0.11, p = 0.12 respectively), no correlation exists. In conclusion, ticagrelor, unlike thienopyridines, is associated with a significant correlation between delay from the last intake and platelet inhibition.