UPDATE ON ANTIPLATELET THERAPY FOR STROKE PREVENTION

Aspirin is effective in reducing vascular outcomes in patients with atherosclerosis, with a relative risk reduction of about 30% for stroke, 22% for stroke and death and 15% for vascular mortality. Apparently 900 and 1,300 mg aspirin are similar in efficacy. Whether low dose aspirin, such as 75 or 30 mg/day, is as effective in preventing strokes is less certain. Complications of high dose aspirin are more frequent than with low doses. The Ticlopidine Aspirin Stroke Study showed, in the 1 st year, a 42% risk reduction for stroke and death and a 47% risk reduction for stroke and stroke death. The superiority of ticlopidine in the reduction in strokes was seen in both males and females. Save for a reversible severe neutropenia in 0.9% of patients on ticlopidine, side effects related to ticlopidine were relatively benign and reversible. The Canadian American Ticlopidine Study compared ticlopidine to placebo in patients with completed major strokes. The primary outcome cluster of stroke, myocardial infarction and vascular death showed a risk reduction of about 30% in the ticlopidine group, providing strong evidence that ticlopidine conveys a clinically important reduction in the risk of thromboembolic events in patients with a history of completed thromboembolic stroke. In conclusion, aspirin is effective in preventing stroke, myocardial infarction and death from vascular causes. Ticlopidine is more effective than aspirin in preventing stroke. The modest, reversible risk of neutropenia, affecting less than 1% of patients, makes the benefit-risk ratio a reasonable one. Meta-analysis of pooled antiplatelet stroke prevention trials and antiplatelet studies in other indications add statistical strength to these observations and yield important new inferences in subgroups of risk, which show the way for improved prevention of the individual patient and for more focused prevention trials in the future.