Clinical experience with low molecular weight heparins.

Low molecular weight heparins (LMWHs) have been prepared by means of different fragmentation or fractionation procedures with the aim of obtaining a more effective and/or safer antithrombotic agent than standard heparin (SH). LMWHs resulting from different production procedures are structurally heterogeneous; this could account for the different efficacy and safety observed clinically. Many clinical trials have been carried out on the prevention of deep-vein thrombosis (DVT) and pulmonary embolism in patients undergoing major abdominal or orthopedic surgery, hemodialysis or affected by non-hemorrhagic stroke. When given once daily, LMWHs are at least as effective in all indications as SH given twice or three times daily and some of them resulted even more effective than SH in general and in orthopedic surgery. The role of LMWHs in the treatment of DVT and their superiority over SH in terms of bleeding remain to be established.