Very low doses of unfractionated heparin potentiate the anti-Xa activity of low molecular weight heparin (enoxaparin)

ABSTRACT

Some previous reports indicated that a minimal amount of anti-IIa is necessary for the optimal anti-Xa activity of low molecular weight heparin (LMW-H). To know if we could improve the prophylactic activity of LMW-H, providing a mild antithrombin effect, we conducted an experiment in which we administered subcutaneously to 10 volunteers, very low doses of unfractionated heparin (UFH), (1000 IU), a LMW-H (enoxaparin, 2000 IU = 20mg), or both heparins together on alternate days, and measure the anti-Xa activity before, and 4 hours after injection. We found that the anti-Xa activity in the first group (UFH), increased by 33%, over the basal values; in the second group (LMW-H), by 93%, but it increased by 282%, in the third group (UFH + LMW-H) showing clearly (p < 0.0069), that UFH could increase synergistically, more than additive, the anti-Xa activity of enoxaparin. The impact on the cost-effectiveness of antithrombotic prophylaxis and the therapeutic results with the herein combined scheme should be evaluated.