Blockade of GPIIb/IIIa by eptifibatide and tirofiban does not alter tissue factor induced thrombin generation in human endotoxemia

Activated platelets facilitate thrombin generation by providing a catalytic surface on which coagulation activation occurs. The glycoprotein (GP) IIb/IIIa receptor might play a major role in this process as shown by in vitro and animal experiments. However, it is controversial whether the GPIIb/IIIa receptor facilitates tissue factor-induced thrombin generation in humans as well. We therefore investigated whether two clinically used GPIIb/IIIa antagonists (tirofiban and eptifibatide) may blunt TF-induced coagulation in humans. Thirty male volunteers received 2 ng/kg endotoxin and standard doses of eptifibatide, tirofiban or placebo over 5 hours in a randomized, double-blind, placebo-controlled, double-dummy parallel-group trial. Markers of thrombin generation (prothrombin fragment 1+2, thrombin-antithrombin complexes), fibrinolysis (D-dimer, plasmin-antiplasmin complexes) as well as inflammatory markers (interleukin-6, tumor necrosis factor-alpha) were measured by enzyme linked immunoasssays,TF-mRNA expression was quantified by RT-PCR. Neither eptifibatide nor tirofiban influenced LPS-induced coagulation activation or fibrinolytic activity. Additionally, the increase of TNF-alpha and IL-6 was similar in all groups. In conclusion, GPIIb/IIIa blockade with eptifibatide or tirofiban did not influence TF-induced coagulation activation in human low grade endotoxemia.