Summary
The anticoagulant effect of selected synthetic inhibitors of thrombin and factor Xa
was studied in vitro in commonly used clotting assays. The concentrations of the compounds
doubling the clotting time in the various assays were mainly dependent on their thrombin
inhibitory activity. Factor Xa inhibitors were somewhat more effective in prolonging
the prothrombin time compared to the activated partial thromboplastin time, whereas
the opposite was true of thrombin inhibitors.
In vivo, in a venous stasis thrombosis model and a thromboplastin-induced microthrombosis
model in rats the thrombin inhibitors were effective antithrombotically whereas factor
Xa inhibitors of numerically similar IQ value for the respective enzyme were not effective
at equimolar dosage
The results are discussed in the light of the different prelequisiles and conditions
for inhibition of thrombin and factor Xa in the course of blood clotting.