The effects of dazoxiben, an inhibitor of thromboxane synthetase, on cold-induced forearm vasoconstriction and platelet behaviour in different individuals.

The effect of dazoxiben, a thromboxane synthetase inhibitor, on cold-induced forearm vasoconstriction was determined in two groups of human volunteers, those in whom dazoxiben abolished the platelet aggregation and release reaction induced by sodium arachidonate (group I) and those in whom it did not (group II). Dazoxiben abolished cold-induced forearm vasoconstriction in group I volunteers but not in those of group II. These results imply a correlation between platelet behaviour and cold-induced changes in vascular tone. In the group I volunteers the effect of dazoxiben on cold-induced vasoconstriction was abolished by 1800 mg of aspirin, but not by 40 mg. Since the lower dose of aspirin inhibits platelet cyclo-oxygenase but has no effect on cyclo-oxygenase in blood vessel walls, it is possible that platelets play no part in the modulation of vascular tone by dazoxiben. It is more likely that the effects of dazoxiben are confined to the vessel wall.