Low molecular weight heparin(oid)s. Clinical investigations and practical recommendations

Unfractionated heparin (UFH) is traditionally used for prevention and treatment of thrombosis. However, its use is associated with a clinically relevant bleeding risk. Low molecular weight heparin(oid) [LMWH] preparations have been designed to improve upon the efficacy and safety ratio of UFH. They have been investigated in clinical studies following the favourable outcome of extensive animal experimentation to determine their efficacy in the prevention and treatment of venous thromboembolism and in arterial thrombotic conditions such as ischaemic stroke, percutaneous transluminal coronary angioplasty (PTCA) and unstable angina. Indeed, an improved efficacy/safety ratio of LMWHs in the prevention of postoperative venous thrombosis in high risk orthopaedic surgery patients has been observed as compared to UFH prophylaxis. No significant differences with respect to antithrombotic efficacy and bleeding complications were observed in patients with relatively lower risk such as in those undergoing general surgery. Subsequently, these agents have been investigated for the treatment of venous thromboembolism. The results of a series of clinical trials reveal that LMWHs are at least as safe and effective as UFH for initial treatment, with the additional advantage of the possibility of home treatment without the requirement of laboratory control and with a reduced risk of heparin-induced thrombocytopenia. Preliminary data suggest that LMHWs may be suitable for thromboprophylaxis in neurosurgery and stroke patients; in addition, they may have a place in the treatment of patients with acute stroke, unstable angina and individuals in the post-myocardial infarction stage. However, additional confirmatory data for these potential indications are required before definite recommendations can be given. LMWH compounds have at least a similar efficacy and safety as UFH in haemodialysis. In addition, they simplify the anticoagulant regimen because of the efficacy of a single predialysis bolus injection.