PREVENTION OF EXPERIMENTAL VENOUS THROMBOSIS IN RABBITS WITH DIFFERENT LOW-MOLECULAR-WEIGHT HEPARINS, DERMATAN SULFATE AND HIRUDIN

In a randomized, blind study the antithrombotic efficacy of dermatan s ulphate (DS), recombinant hirudin (r-hirudin) and four commercially av ailable low molecular weight heparins (LMWHs) was investigated after i ntravenous administration in a jugular vein thrombus model in rabbits utilizing a combination of endothelial damage and flow reduction. The parameters observed were the frequency of visible thrombosis, the freq uency of occlusive thrombosis and thrombus weights. DS and r-hirudin w ere investigated in one fixed dose and the LMWHs in prophylactic doses , adjusted to body weight, recommended in high-risk situations by the manufacturers. All substances effectively reduced the three observed p arameters. DS and r-hirudin were equally or even more effective than t he LMWHs. Although significant differences were not found between the individual LMWH treatments a visible trend cannot be overlooked in all three observed parameters. This cannot solely be explained by the dif ferent antifactor Xa activity doses given but increased antithrombotic activity was observed with declining antifactor Xa/antifactor IIa rat io. Our findings indicate that the different commercial LMWHs may diff er in their antithrombotic activity when given in recommended doses ad justed to body weight in this experimental model. Dose range studies a re required to clarify the thromboprophylactic efficacy of DS and r-hi rudin in relation to the tested LMWHs.