The inhibitory effects of EB-382, a non-steroidal antiinflammatory agent, on platelet aggregation and prostaglandin biosynthesis were studied. EB-382 exhibited a dose-dependent inhibitory effect on the collagen and arachidonic acid-induced rabbit platelet aggregation in vitro, and its IC
50 values were 231.2 and 116.1μM, respectively. The efficacy of EB-382 was about twice less potent than that of ibuprofen. EB-382 exhibited a dose-dependent inhibitory effect on the collagen-induced rat platelet aggregation ex vivo, and its ED
50 value was 62.5mg/kg, p.o. The efficacy of EB-382 was about twice less potent than that of ibuprofen. EB-382 did not affect the ADP-induced platelet aggregation both in rabbits in vitro and rats ex vivo. EB-382 inhibited dose-dependently the arachidonic acid-induced pulmonary thrombotic mortality in mice, and its ED
50 value was 62.9mg/kg, p.o. The efficacy of EB-382 was about twice less potent than that of ibuprofen. EB-382 exhibited a dose-dependent inhibition of prostaglandin synthetase activity, and its IC
50 value was 1.9×10
-4M. The efficacy of EB-382 was about 10 times less potent than that of ibuprofen. These results indicate that EB-382 affect platelet aggregation through the inhibition of the prostaglandin biosynthesis, but its efficacy on the platelet aggregation is fairly less potent, comparing with its inflammatory, analgesic and antipyretic activities.
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