Low molecular weight heparins. An objective overview.

The introduction of low molecular weight heparins has added a new dimension to the management of thrombotic disorders. Ten LMWHs are currently available for clinical use. Although these agents have been primarily developed and used in European countries, other countries, including the US, have started to evaluate their usefulness. Well designed clinical trials have been carried out for different clinical indications with several of these products. In contrast to other prophylactic antithrombotic drugs (heparin, warfarin, aspirin), LMWHs have provided consistently impressive clinical results. Moreover, the other products have less desirable tolerability profiles than that of LMWHs. As shown in both experimental and clinical settings, the prophylactic antithrombotic efficacy of each LMWH is distinct in itself being characteristic to only that particular drug. Besides the currently available LMWH preparations, some 14 other agents are under development at this time. Although both the original and newer products have similar basic characteristics, the physicochemical properties and the pharmacological actions of each of these agents may differ significantly. All manufacturers should follow the Food and Drug Administration (FDA) guidelines and conduct their own clinical trials on each of their products. Many significant developments of LMWHs will take place in the coming years; in addition to development for prophylactic use, LMWHs will be developed for therapeutic intervention.