ADJUSTED VERSUS FIXED DOSES OF THE LOW-MOLECULAR-WEIGHT HEPARIN FRAGMIN IN THE TREATMENT OF DEEP-VEIN THROMBOSIS

Treatment monitoring based on a laboratory parameter increases the eff icacy and safety of standard heparin therapy, but it is not known if t his also applies to low-molecular-weight heparin (LMWH) therapy of acu te deep vein thrombosis (DVT). In a prospective randomized trial invol ving 122 consecutive patients, group A (58 patients) received a weight adjusted dose of Fragmin (100 IU/kg) subcutaneously twice a day throu ghout the treatment period (10 days +/- 1), while in group B (64 patie nts) the dosage was based on the results of an anti factor Xa (anti Xa ) amidolytic assay to obtain a target concentration from 0.5 to I IU/m l. AntiXa and antithrombin activities were also measured retrospective ly on frozen plasma from all patients. The two regimens were comparabl e in terms of hemorrhagic complications (4 in group A and 3 in group B ). Bilateral ascending phlebography was performed before inclusion and at the end of LMWH treatment. Treatment efficacy, based on Marder's s core, did not differ between the two groups (p = 0.3). Dosage adjustme nt to between 0.5 to 1 IU anti-Xa/ml does not therefore appear to impr ove the efficacy or safety of LMWH treatment. However, correlations be tween the change in Marder's score and both anti-Xa (p <0.001) and ant ithrombin activity (p <0.001) were observed, suggesting a relationship between the degree of FXa or thrombin inhibition and antithrombotic a ctivity.