Evaluation of Treatment-Dose Enoxaparin in Acutely Ill Morbidly Obese Patients at an Academic Medical Center: A Randomized Clinical Trial

Background: Enoxaparin dosing recommendations for morbidly obese patients are lacking. Retrospective and observational studies reported goal anti-Xa levels with a median dose of 0.8 mg/kg using total body weight. Further studies are needed to determine if a more conservative dosing strategy is warranted. Objective: To determine if reduced dose enoxaparin was more effective than standard dose at achieving goal anti-Xa levels in morbidly obese patients. Methods: A prospective, randomized, controlled study was conducted in patients with a body mass index (BMI) >= 40 kg/m(2). Patients were randomized to standard (1 mg/kg) or reduced dose (0.8 mg/kg) enoxaparin every 12 hours. The primary outcome was the proportion of patients with an initial anti-Xa at goal (0.5-1.1 IU/mL). Results: A total of 62 patients were enrolled and randomized to 1 mg/kg (n = 32) or 0.8 mg/kg (n = 30), and 54 patients completed the study. The study did not meet accrual for 80% power. Goal anti-Xa levels were achieved in a similar proportion for the reduced-dose (n = 25/28) and standard dose arms (n = 20/26; 89.3% vs 76.9%; P = 0.29). Overall, 9 patients required dose adjustments, of which 6 were in the 1-mg/kg arm, and all were above goal. No documented bleeding or thrombotic events were reported. Conclusions and Relevance: This was the first randomized, controlled trial of enoxaparin dosing in patients with a BMI >= 40 kg/m(2). Overall, 89% of patients had a goal anti-Xa when initiated on 0.8 mg/kg. Based on the results, reduced dose enoxaparin may be a reasonable dosing strategy in morbidly obese patients.