Differential Effects of Clopidogrel With or Without Aspirin on Platelet Reactivity and Coagulation Activation: A Randomized Trial in Healthy Volunteers

Abstract

Dual antiplatelet therapy (DAPT) is standard in acute coronary syndrome but confers a bleeding risk. To compare effects of clopidogrel single antiplatelet therapy (SAPT) with clopidogrel-based DAPT on hemostatic system activation we conducted a randomized clinical trial in 44 volunteers (clopidogrel (d1: 600 mg, d2-6: 150 mg) ± aspirin (100 mg)). Multiple electrode aggregometry-adenosine diphosphate (MEA-ADP) and MEA-arachidonic acid (MEA-AA) triggered aggregometry, vasodilator-stimulated phosphoprotein (VASP), beta thromboglobulin, p-selectin, thromboxane B₂ , d-Dimer, prothrombin fragment 1.2 (f1.2), and a phospholipid-dependent clotting time were measured in venous blood. Changes are described by mean differences (Δmean (95% confidence interval (CI)) or geometric mean ratios (95% CI)). DAPT and SAPT comparably and significantly decreased MEA-ADP at 2 hours (-60% vs. -63%; P = 0.35, Δmean -4.9, 95% CI -15.4 to 5.5). At 24 hours (-59% vs. -47%, P = 0.04, Δmean -11.1, 95% CI -21.7 to -0.4]) and 8 days (-61% vs. -53%, P = 0.04, Δmean -11.3, 95% CI -22.0 to -0.6). Both treatments significantly reduced VASP and MEA-AA after 2 hours and 8 days. DAPT inhibited MEA-AA significantly stronger at 2 hours (-77% vs. -30%; P < 0.0001, Δmean -39.6, 95% CI -54.2 to -25.0), at 24 hours (-80% vs. -27%, P < 0.0001, Δmean -47.8, 95% CI -62.3 to -33.3), and 8 days (-79% vs. -27%, P < 0.0001, Δmean -48.9, 95% CI -62.5 to -35.4). Neither treatment significantly influenced beta thromboglobulin or p-selectin. DAPT abolished and SAPT reduced thromboxane B₂ after 24 hours and 8 days. The d-Dimer was reduced by DAPT (0.94, 95% CI 0.89-1.00, P = 0.04) at 2 hours but not after 24 hours and 8 days. SAPT did not decrease d-Dimer. Neither treatment affected f1.2. DAPT and SAPT comparably affect platelet and coagulation activation in venous blood.