Time course of the antiplatelet effect after switching to clopidogrel from initial prasugrel therapy in patients with acute coronary syndrome.

Prasugrel is often replaced with clopidogrel after a certain period of time following coronary stenting. However, the time course of platelet aggregation during this replacement is unknown. We performed a prospective, single-arm study to monitor platelet reactivity before and after the replacement. Forty-five patients (mean age 62.6 ± 13 years, 40 male) who received coronary stenting for acute coronary syndrome were initially treated with the loading dose (20 mg) of prasugrel followed by the maintenance dose (3.75 mg/day) for 7 days, then switched to 75 mg/day of clopidogrel. The P2Y12 reaction unit (PRU) level was measured at baseline and selected time points. Prasugrel effectively suppressed PRU from 248 ± 59 at baseline to 145 ± 65 on day 1 (P < 0.001). The PRU value on the final day of prasugrel treatment (day 7) was 156 ± 68 (P < 0.001 vs. baseline). After switching to clopidogrel, PRU was consistently suppressed [146 ± 60, 139 ± 54, and 135 ± 60 on days 9, 11, and 13, respectively (P < 0.001, each point vs. baseline)]. Switching from the initial prasugrel therapy to clopidogrel using the maintenance dose does not cause a drug efficacy gap and stays effective for preventing stent thrombosis.