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Clinical Observation
February 14, 2005

Efficacy and Safety of Fixed Low-Dose Dalteparin in Preventing Venous Thromboembolism Among Obese or Elderly Hospitalized Patients: A Subgroup Analysis of the PREVENT Trial

Author Affiliations

Author Affiliations: Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, Mass (Drs Kucher and Goldhaber); Unité de Pharmacologie Clinique, Université Claude Bernard Lyon I, Lyon, France (Dr Leizorovicz); Cardiology Division, College of Medicine, University of Illinois at Chicago, and Medical Development, Pharmacia, Skokie, Ill (Dr Vaitkus); Department of Academic Medicine, Guy’s, King’s and St Thomas’ School of Medicine, London, England (Dr Cohen); Department of Medicine, Hamilton Health Sciences—General Hospital, Hamilton, Ontario, Canada (Dr Turpie); and Verksamhetsområde Akutsjukvård, Universitetssjukhuset, Lund, Sweden (Dr Olsson).

Arch Intern Med. 2005;165(3):341-345. doi:10.1001/archinte.165.3.341

Background  We were concerned that a fixed rather than a weight-based dosing regimen of dalteparin sodium to prevent venous thromboembolism (VTE) might result in decreased efficacy in obese patients and decreased safety in elderly patients.

Methods  We retrospectively performed subgroup analyses using the database from the Prospective Evaluation of Dalteparin Efficacy for Prevention of VTE in Immobilized Patients (PREVENT) Trial, a study of 3706 hospitalized, medically ill patients randomized to receive either dalteparin sodium, 5000 U/d, or placebo. The primary end point was a composite of symptomatic VTE, fatal pulmonary embolism, sudden death, or asymptomatic proximal deep venous thrombosis by day 21. Obesity was defined as a body mass index (calculated as weight in kilograms divided by the square of height in meters) of 30 or greater for men and 28.6 or greater for women.

Results  Overall, 1118 patients (30.4%) were obese and 1226 (33.3%) were 75 years or older. In obese patients, the primary end point occurred in 2.8% of the dalteparin and in 4.3% of the placebo groups (relative risk, 0.64; 95% confidence interval [CI], 0.32-1.28). In patients 75 years or older, the primary end point was reported in 4.2% of the dalteparin and in 8.0% of the placebo groups (relative risk, 0.52; 95% CI, 0.31-0.87). The dalteparin effect for the primary end point (odds ratio, 0.51; 95% CI, 0.32-0.82) was not attenuated when adjusted for age, sex, obesity, history of VTE, and varicose veins. Dalteparin was not associated with an increase in major hemorrhage by day 21 in obese (0% vs 0.7% placebo; P>.99) and in elderly (1.1% vs 0.7%; P = .12) patients.

Conclusion  Our findings suggest that a fixed low dose of dalteparin sodium of 5000 U/d is effective and safe in preventing VTE in obese and elderly hospitalized medical patients.

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