Dynamics of thrombus formation on an artificial surface in vivo. Effects of antithrombotic agents.

A nonhuman primate model for in vivo evaluation of antithrombotic agents is described. In this model, the formation of a thrombus on a segment of Silastic tubing placed in the vena cava of a rhesus monkey is utilized to evaluate the effectiveness of antithrombotic agents. Thrombus formation in this model was found to occur rapidly, but this initial deposit quickly was followed by a reduction in thrombus weight. Eventually, after 2 hours of implantation of the test device, thrombus weight again increased and reached an apparent plateau. Three different antithrombotic agents were evaluated with this model. Warfarin therapy was found to decrease the thrombus weight in approximate proportion to its effect on the prothrombin time. Aspirin and dextran each produced a decrease in thrombus weight in 2 of 3 animals tested. Individual differences in response to thrombotic agents are apparent, but despite this, the model appears to offer advantages for in vivo evaluation of antithrombotic agents.