Experimental venous thrombosis in rats treated with heparin and a low molecular weight heparin fraction.

An unfractionated mucosal heparin preparation and a low molecular weight heparin fraction were randomly administered to rats subcutaneously. This injection was made on rats with experimentally induced venous thrombosis. At high doses (6.66 mg/kg) of both drugs, thrombus mean weight was reduced in comparison with a control group. At lower doses (2.22 mg/kg) these two drugs inhibited the growth of the thrombus. This inhibition was obtained with a lower dose (0.66 mg/kg) of the low molecular weight heparin fraction than of heparin. The low molecular weight heparin fraction (molecular weight 5,000 daltons) has a high anti-Xa activity (200 units) and a low activity determined by the USP assay (50 units).