Trial of dipyridamole-aspirin in recurring venous thrombosis.

38 patients (26 men) with recurring venous thromboembolism (RVTE) were enrolled in a prospective double-blind, placebo-controlled trial of dipyridamole (DPY), 100 mg a day, and aspirin (ASA), 1200 mg a day. Platelet survival (51Cr labelling of autologous platelets) was measured every 6 months for 18 months. 19 patients were randomised to treatment with DPY and ASA, and 1 had new venous thrombosis (after 15 months of treatment); 19 received placebo and 7 had new venous thrombosis (4--16 months later (chi 2 = 5.70; p< 0.05). DPY-ASA increased platelet survival whereas placebo treatment did not. The results suggest that in patients with RVTE and abnormal platelet survival time DPY in combination with ASA decreases the frequency of new venous thrombosis. Peptic ulcers developed in 2 patients treated with DPY-ASA.