Experimental studies on the antithrombotic and haemorrhagic effects of heparin and a low molecular weight heparin derivative.

Antithrombotic, haemorrhagic and anticoagulant effects of unfractionated heparin (UH) and the low molecular weight heparin fragment KABI 2165 were studied in rats. In stasis-induced venous thrombosis of the jugular vein intravenous injection of both, UH and KABI 2165, either reduced significantly the size of thrombi or completely prevented thrombus formation in a dose-dependent manner. The dose of KABI 2165 required for prevention of thrombus formation showed a marked anticoagulant activity measured by APTT which was in the same range as that of the equieffective dose of UH. After administration of antithrombotically effective doses only UH caused a significant prolongation of bleeding time after standardized incision of the tail. KABI 2165 produced haemorrhagic effects at about 4-fold higher doses only than those required for the antithrombotic action.