Platelet deposition on human atherosclerotic lesions is decreased by low-dose aspirin in combination with dipyridamole.

Eighteen patients with ischaemic peripheral vascular disease were treated for a 5-week period with either 20 mg aspirin daily, 75 mg dipyridamole three times daily or a combination of these two treatments. Before and after 4 weeks' treatment autologous platelet labelling with 111In was carried out and sites of active vascular platelet uptake monitored, and platelet half-life measured. Neither aspirin nor dipyridamole alone had any effect on platelet uptake or on platelet half-life. The combination of aspirin and dipyridamole resulted in a significant decrease in platelet uptake and a nonsignificant trend towards prolongation of platelet half-life. These findings suggest that this combined therapy may be of benefit in the treatment of atherosclerosis in man.