Increased platelet inhibition after switching from prasugrel to low-dose ticagrelor in Japanese patients with prior myocardial infarction

Abstract

BackgroundTicagrelor and prasugrel are novel and potent P2Y12 inhibitors. Ticagrelor 90mg or 60mg twice daily is known to reduce ischemic events but be associated with an increased risk of bleeding in patients with prior myocardial infarction in Western countries. Although ticagrelor 90mg twice daily was tested in a randomized clinical trial in East Asia, the clinical significance of ticagrelor 60mg twice daily is unclear. This study aimed to evaluate platelet inhibition of low-dose ticagrelor compared to prasugrel in Japanese patients. MethodsA total of 33 patients with prior myocardial infarction (>3 months) who received aspirin and prasugrel 3.75mg once daily were enrolled. Prasugrel was switched to ticagrelor 60mg twice daily. Platelet inhibition was assessed by VerifyNow assay (Accumetrics, San Diego, CA, USA) at baseline and 14 days after switching to ticagrelor. P2Y12 reaction unit (PRU) ≤95 was defined as low on-treatment platelet reactivity (LPR) and PRU≥262 as high on-treatment platelet reactivity. ResultsTicagrelor treatment resulted in significantly lower PRU [10 (7–39) vs. 143 (102–201), p<0.001] and a higher rate of LPR (94% vs. 24%, p<0.001), compared to prasugrel treatment. Neither patients treated with ticagrelor nor prasugrel had high on-treatment platelet reactivity. During 2-week follow-up on ticagrelor therapy, no major bleeding occurred in both groups, while four minor bleeding events were observed. ConclusionIn Japanese patients with prior myocardial infarction, significantly lower PRU and a higher rate of LPR were observed on ticagrelor 60mg twice daily compared to prasugrel 3.75mg once daily.