A topic in Clinical Evidence summarizes the evidence on dipyridamole plus aspirin in people with prior ischaemic stroke or transient ischaemic attack. One systematic review (search date 1997, 25 RCTs, 10 404 people) found that adding dipyridamole to aspirin non-significantly reduced vascular events (not just stroke) compared with aspirin alone (11.8% vs 12.1%, OR 0.94, 95% CI 0.83 to 1.06). Effects on stroke were not certain. Overall, the review found that combination treatment reduced non-fatal strokes (3.5% vs 4.5%, OR 0.76). Most non-fatal stroke events occurred on one large trial (about 6000 people) comparing aspirin (only 50 mg daily) versus dipyridamole (400 mg daily) versus both or neither. Combination treatment did not reduce stroke compared to aspirin alone in other trials. These conflicting results may be because of the lower aspirin dose in the larger trial, or the antihypertensive effect of dipyridamole.