Summary
1. Aromatic diamidines which are potent inhibitors of trypsin possess a marked inhibitory
effect on the clotting activity of human thrombin and on the prothrombin time and
partial thromboplastin time of human plasma. They also block the contact activation
phase of the coagulation process. The strongest inhibitor among the compounds tested
was M & B 4596 which was followed in second place by pentamidine.
2. Pentamidine was 10 times more active than ε-ACA in impeding streptokinase-induced
lysis of human plasma clots. It was 100-200 times stronger than ε-ACA in inhibiting
the activation of bovine plasminogen by activators formed from the interaction between
streptokinase and either human plasmin(ogen) or human plasma.
3. The prothrombin time and partial thromboplastin time of canine plasma were less
susceptible to inhibition by pentamidine than the same tests on human plasma. Clot
lysis in the canine system was inhibited by pentamidine to a similar degree as in
the human system. After intravenous injection of pentamidine in the dog there occurred
the expected prolongation of the partial thromboplastin time and of the clot lysis
time.
