Antiplatelet agents and randomized trials

Patients who have transient ischemic attack (TIA) or ischemic stroke are at a high risk of having a first or recurrent stroke. The annual risk is between 5% and 15%; the risk is highest in the first 48 hours following a TIA and highest in the first 7 days following an ischemic stroke. Secondary prevention includes antithrombotic therapy, treatment of risk factors, and interventional treatment of carotid stenosis. Antithrombotic options can include antiplatelet drugs such as aspirin, aspirin plus extended-release dipyridamole (ER-DP), clopidogrel, or clopidogrel plus aspirin. Oral anticoagulation is used in patients with a cardiac source of embolism such as atrial fibrillation. Aspirin monotherapy offers a modest risk reduction for recurrent stroke and for the combined endpoint of nonfatal stroke, myocardial infarction (MI), and vascular death. The combination of ER-DP and aspirin was shown to be superior to aspirin monotherapy in several trials. Clopidogrel is superior to aspirin in high-risk patients suffering from stroke, MI, or peripheral arterial disease. The combination of clopidogrel plus aspirin is not superior to aspirin or clopidogrel monotherapy and carries a significantly higher bleeding risk. The combination might offer benefit in short-term secondary prevention after TIA or stroke. Another ongoing trial is currently investigating the possible benefit and side effects of aspirin plus ER-DP versus clopidogrel in secondary stroke prevention.