Ischemic and Bleeding Events Among Patients With Acute Coronary Syndrome Associated With Low-Dose Prasugrel vs Standard-Dose Clopidogrel Treatment

IMPORTANCE: Prasugrel was approved at a lower dose in 2014 in Japan than in the West because East Asian patients are considered more susceptible to bleeding than Western patients. However, real-world outcomes with low-dose prasugrel treatment remain unclear. OBJECTIVE: To investigate the association of low-dose prasugrel vs standard-dose clopidogrel administration with short-term outcomes among patients with acute coronary syndrome undergoing percutaneous coronary intervention (PCI). DESIGN, SETTING, AND PARTICIPANTS: This study used data from the Japan Cardiovascular Database–Keio Interhospital Cardiovascular Studies registry, a large, ongoing, multicenter, retrospective cohort of consecutive patients who underwent PCI. The present cohort study evaluated 2770 patients with acute coronary syndrome who underwent PCI and received either low-dose prasugrel (loading dose, 20 mg; maintenance dose, 3.75 mg) or clopidogrel (loading dose, 300 mg; maintenance dose, 75 mg) in combination with aspirin between 2014 and 2018. Propensity score–matching analysis was conducted to balance the baseline characteristics of patients receiving low-dose prasugrel and those receiving clopidogrel. Data analysis was conducted in June 2019. EXPOSURES: Prescription of either low-dose prasugrel or standard-dose clopidogrel prior to PCI. MAIN OUTCOMES AND MEASURES: Primary ischemic events (in-hospital death, recurrent myocardial infarction, and ischemic stroke) and primary bleeding events, defined as bleeding complications within 72 hours after PCI consistent with the National Cardiovascular Data Registry CathPCI Registry definition. RESULTS: Of 2559 patients included in the study, the mean (SD) age was 67.8 (12.7) years, and 78.2% were male. In total, 1297 patients (50.7%) received low-dose prasugrel, and 1262 patients (49.3%) received clopidogrel. After propensity score matching, primary ischemic events among patients receiving low-dose prasugrel and those receiving clopidogrel were comparable (odds ratio [OR], 1.42; 95% CI, 0.90-2.23), but primary bleeding events were significantly higher among patients receiving prasugrel (OR, 2.91; 95% CI, 1.63-5.18). This increase in bleeding events was associated with the presence of a profile of high-bleeding risk (≥75 years of age, body weight <60 kg, or history of stroke or transient ischemic attack) (OR, 4.08; 95% CI, 1.86-8.97), being female (OR, 3.84; 95% CI, 1.05-14.0), or the presence of ST-segment elevation myocardial infarction (OR, 2.07; 95% CI, 1.05-4.09) or chronic kidney disease (OR, 4.78; 95% CI, 1.95-11.7). CONCLUSIONS AND RELEVANCE: Since its approval, low-dose prasugrel has been used by nearly 80% of patients who undergo PCI. Despite the modified dose, bleeding events were higher among patients receiving low-dose prasugrel than among patients receiving clopidogrel, with no difference in ischemic events between the 2 groups. These results suggest the importance of a risk assessment of bleeding prior to selecting a P2Y12 inhibitor, even for the use of a lower approved dose, when treating patients of East Asian descent.