Aprotinin and tranexamic acid are commonly used antifibrinolytics during liver transplantation, or cardiac surgery. However, it is not clear which drug is more effective to ameliorate the fibrinolysis. The aim of the study was to investigate the antifibrinolytic effect of both drugs at previously reported blood concentration and dose.

After inducing fibrinolysis by administering recombinant tissue plasminogen activator to rabbits, we checked the in vitro and in vivo antifibrinolytic effects at previously reported blood concentration and dose, and determined the minimum antifibrinolytic blood concentration. The previously reported blood concentration was 200 KIU/ml for aprotinin and 10 mcg/ml for tranexamic acid, and the previously reported dose was 4 mg/kg bolus plus 1 mg/kg/hr infusion for aprotinin and 10 mg/kg bolus plus 1 mg/kg/hr for tranexamic acid.

In vitro experiment, there was effective antifibrinolytic action at previously reported blood concentration of aprotinin and the minimum antifibrinolytic blood concentration was 40 KIU/ml. For tranexamic acid, there was no antifibrinolytic action at previously reported blood concentration and the minimum antifibrinolytic blood concentration was 100 mcg/ml. In vivo experiment, there was antifibrinolytic action at previously reported dose of aprotinin and the minimum antifibrinolytic dose was 60% of previously reported dose. For tranexamic acid, there was no antifibrinolytic action at previously reported dose and the minimum antifibrinolytic dose was 10 times previously reported dose.

The previously reported blood concentration and dose of aprotinin were greater and those of tranexamic acid were less than the minimum antifibrinolytic blood concentration and dose.