Comparison between the efficacy of prostacyclin analogue (beraprost) with low-dose aspirin and aspirin alone to platelet aggregation and serum prostanoids (thromboxane B₂ and 6-ketoPGF_1α)

Abstract

Recently, low-dose aspirin therapy for preventing cerebral thrombosis has become a popular procedure, based on the fact that high-dose aspirin would induce aspirin dilemma because aspirin inhibits the cyclooxygenase activity of not only platelets but also endothelial cells. However, even low-dose aspirin therapy is not sufficient to improve aspirin dilemma satisfactorily. We attempted to correlate the changes in platelet aggregability and serum prostanoids (6-ketoPGF_1α and thromboxane B₂) in the same patients while they were taking aspirin alone and while they were taking aspirin with beraprost (60 μg per day). The platelet aggregation was measured with an aggregometer using platelet-rich plasma with ADP (2.0 μM) and collagen (2.0 μg/ml). The serum 6-ketoPGF_1α and thromboxane B₂ were determined by radioimmunoassay. No difference was noted in the ADP-induced platelet aggregation, but the collagen-induced platelet aggregation was markedly inhibited by aspirin with beraprost. Concerning the prostanoids, no significant difference was noted in the levels of 6-ketoPGF_1α, but there was significant decrease in the levels of thromboxane B₂. The ratio of 6-ketoPGF_1α/thromboxane B₂, which is a useful parameter for judging the effects of antiplatelet agents, tended to become elevated but not significantly, while patients were taking aspirin and beraprost. In conclusion, low-dose aspirin together with beraprost may be more useful for avoiding dilemma than just aspirin alone.