Low-molecular-weight, unfractionated heparin similarly effective for treating VTE

Subcutaneous injections of unfractionated heparin may be suitable for outpatient VTE treatment.

Subcutaneous injections of unfractionated heparin are equally effective as subcutaneous low-molecular-weight heparin injections for preventing venous thromboembolism recurrence, a randomized study shows.

Based on the results, the authors estimate that drug costs for 6 days of treatment with low-molecular-weight heparin would be $712, while unfractionated heparin would cost just $37 — assuming both drugs are administered according to the study's protocol.

"I think that there's a potential for everyone to benefit from the findings providing the costs are a concern," Clive Kearon, MB, PhD, head of the clinical thrombosis service at Henderson General Hospital, Ontario, and lead author of the study, told Orthopedics Today.

"[Fixed-dose] subcutaneous unfractionated heparin is as effective and safe as low-molecular-weight heparin for initial treatment of patients with venous thromboembolism (VTE) and is suitable for treatment at home," the authors said in the study.

Kearon and colleagues at McMaster University, Hamilton; McGill University, Montreal; and at the University of Auckland, New Zealand, conducted the open-label, adjucator-blinded, noninferiority trial involving 697 patients with acute VTE.

The study was conducted from September 1998 through February 2004 at six university-affiliated clinical centers in Canada and New Zealand. Patients in the trial received either unfractionated or low-molecular-weight heparin administered subcutaneously every 12 hours. All patients also received at least 3 months of warfarin treatment, according to the study.

Researchers assigned 345 patients to receive unfractionated heparin and 352 patients to receive low-molecular-weight heparin. Overall, 80% of patients had symptomatic deep venous thromboembolism (DVT) without pulmonary embolism (PE) symptoms; 19% had symptomatic PE and 1% had asymptomatic DVT, according to the study.

Unfractionated heparin was administered for a mean of 6.3 days and low-molecular-weight heparin was administered for a mean of 7.1 days. Researchers stopped treatment before day 5 for 85 unfractionated heparin patients and for 44 low-molecular-weight heparin patients, "most commonly because the international normalized ratio was greater than 3.0," the study authors said.

The researchers noted a similar incidence of recurrent thromboembolism between the two treatment groups. At 3 months' follow-up, 3.8% of the 345 unfractionated heparin-treated patients and 3.4% of the 352 low-molecular-weight heparin-treated patients experienced recurrent VTE. Both groups also had a comparable rate of major bleeding, according to the study.

Only one patient prematurely stopped using the drug due to thrombocytopenia. This patient was receiving low-molecular-weight heparin; investigators did not suspect heparin-induced thrombocytopenia, the authors noted.

At the time of diagnosis, 68% of patients were receiving care as outpatients. During the course of the study, 72% of unfractionated heparin patients and 68% of low-molecular-weight heparin patients received treatment entirely as outpatients, according to the study.

For more information:
Kearon C, Ginisberg JS, Julian JA, et al. Comparison of fixed-dose weight-adjusted unfractionated heparin and low-molecular-weight heparin for acute treatment of venous thromboembolism. JAMA. 2006;296:935-942.