The antithrombotic effect of thromboxane receptor antagonist HN 11500 on thrombus formation in laser thrombosis model and platelet function tests.

The effect of thromboxane receptor antagonist HN 11500 (Chemie Linz AG, Austria) on thrombus formation in laser thrombosis model and platelet function test has been studied. In this study HN 11500 was a potent antithrombotic agent significantly inhibiting thrombus formation in venules in doses higher than 5 mg/kg after i.v. and 10 mg/kg after oral administration. Lower doses were needed to obtain the same antithrombotic effect when arterioles were investigated. The antithrombotic effect of minimal effective doses of HN 11500 lasted longer than 8 hours in venules and more than 12 hours in arterioles. After oral feeding of this thromboxane receptor antagonist in doses 5 mg/kg, antithrombotic effect in investigated arterioles lasted longer than 16 hours but less than 20 hours. When different doses of HN 11500 were injected i.v. together with r-Hirudin or LMWH CY 216 the inhibitory effect on thrombus formation in venules was stronger and observed with lower doses of HN 11500. In vitro study HN 11500 inhibited platelet adhesion to the siliconized glass, bovine extracellular matrix as well as ADP and collagen mediated platelet aggregation. Lower concentration of this agent were needed to inhibited platelet adhesion to the extracellular matrix than platelet adhesion to the siliconised glass, and ADP and collagen induced aggregation.