Population-based effectiveness and safety of different antiplatelet regimens as secondary prevention for ischemic stroke/Transient ischemic attack

Background: Different antiplatelet regimens are used for secondary prevention after ischemic stroke (IS)/transient ischemic attack (TIA), but studies on the relative effectiveness and safety of each regimen in daily practice are lacking. Objectives: To assess the relative effectiveness and safety of several antiplatelet regimens as secondary prevention in patients after an IS/TIA in clinical practice. Methods: A cohort study was conducted using the Clinical Practice Research Datalink. Patients aged ≥ 18 years with a first diagnosis of IS/TIA in 1998- 2013 were identified. Antiplatelet exposure was categorized into aspirin-dipyridamole, aspirin-only, clopidogrel-only, aspirin-clopidogrel, other regimens, and no-antiplatelet exposure. The primary effectiveness outcome was a composite endpoint of nonfatal IS, nonfatal myocardial infarction (MI), or cardiovascular (CV) death; and the safety outcome was major bleeding. Time-dependent Cox regression analysis was used to assess the association between antiplatelet regimens and CV effectiveness and major bleeding outcomes. Results: We followed 20,552 IS/TIA patients for a median duration of 2.3 years. There were 5,714 composite events during follow-up. All regimens were effective in reducing the primary effectiveness outcome compared to no-antiplatelet exposure. Aspirin-only, clopidogrel-only, aspirin-clopidogrel and other regimens were significantly (p <0.05) less effective compared to aspirin-dipyridamole (HR: 1.35, 1.12, 1.40, and 1.27, respectively), adjusted for age, sex, lifestyle factors, disease history and CV comedications. All other regimens were also significantly (p <0.05) associated with a higher relative risk of major bleeding compared to aspirin-dipyridamole (HR: 1.21, 1.32, 1.78, and 1.37, respectively), adjusted for age, sex, alcohol use, liver and renal disease, major bleeding history and comedications. Conclusions: Compared to aspirin-dipyridamole, all other antiplatelet regimens are less effective in reducing the risk of nonfatal IS, nonfatal MI or CV death, and associated with a higher risk of major bleeding in patients with IS/TIA.