[Which antithrombotic agents should be prescribed in deep venous thrombosis of the limbs?]

Anticoagulants are generally prescribed for the treatment of thrombosis occurring in deep veins. Recent progress in both heparin therapy and in antivitamin K agents require a new look at the therapeutic choice. Due to its immediate anticoagulant action heparin is essential as first intention therapy. Indeed, initial oral anticoagulants are less effective, both in terms of clinical extension and in radiological outcome, than an initial heparin/antivitamin K combination. Non-fractionated heparin administered with an automatic syringe after a priming bolus is the reference treatment for venous thrombosis since it has now been established that 2 subcutaneous injections of heparin are less effective than the intravenous route. Both the effect and safety of low molecular weight heparin have been shown to be comparable with that of non-fractionated heparin. When the dose is adapted to patient weight, 70% are within therapeutic limits after the first injection. Two daily injections of 100 IU per kg body weight can be recommended as initial treatment for deep vein thrombosis. Anticoagulation must be continued for several days but the risk of induced thrombocytopenia persists with low molecular weight heparin. Long-term use should be retained essentially for pregnant women with deep vein thrombosis due to the foetal risk of oral antivitamin K. Antivitamin K oral agents may be initiated early without hindering the anticoagulant effect of heparin. With oral agents, anticoagulant equilibrium is reached, on the average, after 6 days and is a function of vitamin K-dependent half-lives. Since antivitamin K agents affect the stability of prothrombin times during the day/night cycle, it has been recommended to favour long half-life molecules. Standardized prescription protocols can improve safety and anticoagulant equilibrium. To date, the recommended management of deep vein thrombosis includes combining low molecular weight heparin and long half-life antivitamin K. Further progress may be forthcoming with the development of new antithrombotic agents such as hirudine or sulfated heparanes.