Contrary to oral warfarin therapy, the use of subcutaneous low-molecular weight heparin (LMWH) has the advantage of stable dosing without the need of prothrombin time monitoring. Few randomized studies have compared the efficacy of LMWH with the least costly unfractionated heparin for the treatment of deep vein thrombosis (DVT). In the United States, 6 days of LMWH therapy for an 80 kg patient is estimated to cost $712, compared with $37 of unfractionated heparin.
In the August 23 issue of JAMA, Kearon and colleagues from the Fixed Dose Heparin Investigators (FIDO) report the results of a randomized trial comparing the efficacy and safety of fixed-dose, weight-adjusted unfractionated heparin to LMWH in the treatment of DVT.
A total of 708 patients with DVT were randomized into two groups. One group received an initial dose of 333 U/kg of unfractionated heparin followed by a fixed dose of 250 U/kg every 12 hours. LMWH (dalteparin or enoxaparin) was administered at a dose of 100 IU/kg every 12 hours. An equal percentage of patients in each group had a history of malignancy (16%) or pulmonary embolus (19%). Forty-two percent of patients were female.
At the completion of the study, there were no statistically significant differences between the unfractionated heparin and LMWH groups with regards to recurrent DVT (3.8% vs. 3.4%) or major bleeding (1.1% vs. 1.4%). Treatment was completed as an outpatient in 72% and 68% of groups, respectively.
This study shows that fixed-dose, weight-adjusted, unmonitored dosing of subcutaneous unfractionated heparin is equally efficacious and safe when compared to low-molecular weight heparin for the treatment of DVT.