[Duodenal absorption of a low molecular weight heparin in rabbits]. / Absorption duodénale d'une héparine de bas poids moléculaire chez le lapin.

Commercial heparin cannot practically cross the intestinal barrier. Meanwhile, because of the theoretical interest in oral heparin therapeutics, we applied our studies to a low molecular weight heparin fraction (3 000 to 4 000 D). This fraction was directly injected into anaesthetized rabbit duodenum. For an equal anticoagulant activity (expressed in international units), commercial heparin is not absorbed whereas the low molecular weight fraction mainly induces an early plasmatic anti-Xa activity which remains over the fifth hour.

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).