Prevention of thromboembolic disease in general surgery with enoxaparin (Clexane)

Different low molecular weight heparins have been compared with unfractionated heparin for the prevention of venous thrombosis in general surgery in about 20 controlled therapeutic trials since 1984. The Multicentre Genox Study* included 892 patients in three consecutive randomized studies with a daily dose of 60, 40 and 20 mg of enoxaparin, respectively, the first injection given 2 h prior to surgery, as compared to subcutaneous unfractionated heparin 5000 IU tds. All included patients had at least one additional risk factor for thrombosis, in addition to surgical risk and to age over 40 years. This trial was the first to compare low molecular weight heparins to controls receiving three daily injections of unfractionated heparin instead of two, and to use three different daily doses of a low molecular weight heparin. The trials were conducted in abdominal, gynaecologic, urologic and thoracic surgery. About 30% of patients had malignancy. Percentages of positive 125I-fibrinogen uptake test (isotopic thrombosis) were comparable: 2.9, 2.8 and 3.8% with enoxaparin and 3.8%, 2.7% and 7.6% with unfractionated heparin, and were not significantly different. There was a significant decrease in haematocrit and haemoglobin only in those patients receiving 60 mg of enoxaparin. The conclusion of this study was that a daily dose of 20 or 40 mg of enoxaparin (approximately 2000 and 4000 anti-Factor Xa IU) was safe and not statistically different from unfractionated heparin. No biological control, except platelet counts before treatment and then twice a week, is required in prophylaxis.