Antiplatelet effects of intravenous iloprost in patients with peripheral arterial obliterative disease. A placebo-controlled dose-response study.

The dose-dependent inhibition of platelet aggregation by the chemically stable, prostacyclin-mimetic, iloprost, was studied in patients suffering from stage II-III peripheral arterial obliterative disease (PAOD). The study was designed as a randomized placebo-controlled cross-over trial. Iloprost was administered i.v. to six patients at doses of 0.5, 1.0, 2.0 or 3.0 ng/kg X min for 4 h, with an interval of 2-3 days between the infusions. During iloprost infusion, systolic and diastolic arterial blood pressure, heart rate and blood flow in the affected limb remained unchanged. In contrast, there was a considerable, dose-dependent inhibition of ADP- and thrombin-induced platelet aggregation and secretion ex vivo at doses of 0.5-2.0 ng/kg X min iloprost, indicating that iloprost reduced platelet stimulation by 50%-70%. The antiplatelet action of iloprost remained unchanged during infusion but ceased with 2 h after administration had ended. The agent was tolerated by the patients without unacceptable side-effects at doses up to 2 ng/kg X min. It is concluded that iloprost administered i.v. at doses of 1-2 ng/kg X min in patients with stage II-III PAOD does not involve haemodynamic side-effects and might be considered an effective antiplatelet agent.