Prophylactically Effective Doses of Enoxaparin and Heparin Inhibit Prothrombin Activation

Results of randomized clinical trials have demonstrated that unfractionated (UF) and low molecular weight (LMW) heparins reduce the frequency of post-operative deep vein thrombosis (DVT) and pulmonary embolism1–6. UF and LMW heparins are given by subcutaneous injection 2–12 hours pre-operatively, and the injections are then continued for up to 10 days. The prophylactic injections can also begin post-operatively. Prophylactic use of UF and LMW heparins can reduce the incidence of post-operative DVT by up to 70%1–8. UF and LMW heparins are also used to initiate the treatment of deep vein thrombi and pulmonary embolism9,10. The need to administer UF or LMW heparins for up to 10 days (to prevent post-operative DVT or to treat established DVT) suggests that the stimuli which contribute to the establishment and propagation of clinically significant thrombi persist for several days.