Ketanserin (S2-receptor blocking agent), platelet activity and chronic alcoholism.

Ketanserin is a pure and selective antagonist of serotonin S2-receptors in blood vessels, platelets and bronchial tissue. It antagonizes serotonin-induced vasoconstriction, bronchoconstriction and platelet aggregation, and indirectly it blocks platelet release reaction. Ketanserin has little or no effect on healthy subjects. Serotonin-induced or serotonin-potentiated platelet aggregation is inhibited in blood drawn from ketanserin-treated healthy volunteers. Oral or parenteral ketanserin treatment did not cause major changes in beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) plasma concentrations, when basic values were normal. Increased microaggregate formation was found in alcoholics and heavy drinkers. It was also found that beta-TG and PF4 levels were higher in these patients than in the controls. Ketanserin treatment tended to normalize these protein levels in such patients.