Impact of Low-Dose Prasugrel on Platelet Reactivity in Chronic Phase of Post-Percutaneous Coronary Intervention (CHAPERON): a Prospective Cohort Study.

Purpose: Asians often face the problems of clopidogrel resistance and East Asian paradox. This study aimed to evaluate the effects of P2Y inhibitors, including low-dose prasugrel 2.5 mg, on the P2Y reaction unit (PRU) in the chronic phase after percutaneous coronary intervention (PCI).

Methods: A total of 348 patients were studied. PRU was measured 6-12 months after PCI and subsequently, 6 months later using a P2Y assay, respectively. This study evaluated the proportion of bleeding risk (PRU ≤ 85) and ischemic risk (PRU ≥ 239) as primary endpoints, and the prediction of bleeding risk and ischemic risk using multivariable logistic regression analysis.

Results: At baseline, 136 patients (39%) received prasugrel 3.75 mg, 48 patients (14%) received prasugrel 2.5 mg, and 164 patients (47%) received clopidogrel 75 mg. Clopidogrel 75 mg had a significantly higher proportion of ischemic risk within one year after PCI than the other groups, and was an independent predictor for ischemic risk with reference of prasugrel 3.75 mg. In addition, switching from clopidogrel 75 mg to prasugrel 2.5 mg significantly lowered and aggregated the PRU value. Whereas, dose reduction of prasugrel had a significantly lower proportion of bleeding risk over one year after PCI than the continuation of prasugrel 3.75 mg, and was an independent predictor for bleeding risk with reference of continuation of prasugrel 3.75 mg.

Conclusions: Prasugrel 2.5 mg has a lower ischemic risk and a more stable PRU value compared with clopidogrel treatment. Prasugrel also contributes to a decline in bleeding risk with concomitant dose reduction.

Trial Registration: University Hospital Medical Information Network (UMIN), ID: UMIN000029541, Date: October 16, 2017 ( https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000033395 ).