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.