Switching Patients from Clopidogrel to Prasugrel in Acute Coronary Syndrome: Impact of the Clopidogrel Loading Dose on Platelet Reactivity

Objectives The present study aimed to assess the pharmacodynamic response of a prasugrel 60‐mg loading dose (LD) alone compared with prasugrel 60 mg added to clopidogrel 600 mg. Background Patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI) commonly receive a clopidogrel LD prior to angiography. Switching these patients to prasugrel may be desirable because higher platelet inhibition is expected. Methods In this open‐label, multicenter, nonrandomized trial, 75 patients were categorized into 2 treatment strategies: Those who received a clopidogrel 600‐mg LD and received a reloading dose of prasugrel 60 mg (clopidogrel/prasugrel group) and those who did not receive a clopidogrel LD and received a prasugrel 60‐mg LD (prasugrel group). Platelet reactivity was assessed using VerifyNow P2Y12 reaction units (PRU) and Platelet Reactivity Index vasodilator‐stimulated phosphoprotein phosphorylation (PRI‐VASP) at 3 different times: at the sheath insertion prior to prasugrel LD, 4 hours after prasugrel LD, and at discharge. Results Four hours after prasugrel LD, platelet reactivity did not differ between the clopidogrel/prasugrel group and the prasugrel group according to the VerifyNow assay (median PRU 23 [5–71] vs. 54 [5–91], respectively; P = 0.18) and the VASP assay (median PRI 8.67 [4.51–16.85] versus 8.03 [4.82–21.72], respectively; P = 1.0). No significant differences in PRU and PRI were observed at discharge. Few bleeding events were reported without any significant differences between the 2 groups. Conclusions Platelet reactivity with prasugrel 60 mg added to a clopidogrel 600‐mg LD was not significantly different compared with prasugrel 60 mg alone in ACS patients undergoing PCI. (J Interven Cardiol 2014;27:365–372)