Weight-based dosing of enoxaparin for VTE prophylaxis in morbidly obese, medically-Ill patients

In clinical trials, fixed-dose enoxaparin (40 mg once daily) reduces the risk of venous thromboembolism (VTE) in medically-ill patients. However, morbidly obese patients were under-represented in these trials and using fixed-dose enoxaparin in obese patients may be inadequate. We completed a pharmacokinetic study in morbidly obese, medically-ill patients to determine if weight-based dosing of enoxaparin for VTE prophylaxis was feasible, without excessive levels of anticoagulation, as determined by peak anti-Xa levels.

Twenty eight morbidly obese (BMI>or=35 kg/m(2)) patients were enrolled and completed the study protocol. Enoxaparin 0.5 mg/kg was administered once daily subcutaneously and peak anti-Xa levels were measured approximately 4-6 hours after the enoxaparin dose.

Overall, 46% of patients were female, the average age (+/-SD) was 54 (+/-11) years, and the average weight and BMI were 135.6 kg (+/-25.3) and 48.1 kg/m(2) (+/-11.1), respectively. The average daily dose of enoxaparin was 67 mg (+/-12). The average peak anti-Xa level was 0.25 (SD+/-0.11, range 0.08 to 0.59) units/mL. Peak anti-Xa levels did not significantly correlate with weight or BMI. There were no bleeding events, symptomatic VTE, or significant thrombocytopenia. In morbidly obese, medically-ill patients, use of weight-based enoxaparin dosed at 0.5 mg/kg once daily is feasible and results in peak anti-Xa levels within or near recommended range for thromboprophylaxis, without any evidence of excessive anti-Xa activity. These data suggest that this weight-based regimen may be more effective than standard fixed-dose enoxaparin. Clinical outcome studies are warranted to determine the clinical safety and efficacy of this regimen.