Assessing an enoxaparin dosing protocol in morbidly obese patients

The effect of obesity on the pharmacokinetics of enoxaparin is not clearly understood and traditional treatment doses in morbidly obese patients (body mass index [BMI] > 40 kg/m2) can lead to over anticoagulation. Our institution developed an inpatient protocol with reduced enoxaparin doses (0.75 mg/kg/dose based on actual body weight) for patients with a weight >200 kg or BMI > 40 kg/m2. The primary objective was to determine if modified enoxaparin treatment doses would achieve therapeutic anti-Xa levels (goal range 0.6–1.0 IU/mL) in morbidly obese patients. Thirty-one patients were included in our study and had a median body weight of 138 kg (range 105–197) and a median BMI of 46.2 kg/m2 (range 40.1–62). The initial peak anti-Xa levels were in therapeutic range in 15 of 31 patients (48 %) with an initial mean anti-Xa level of 0.92 IU/mL. Twenty-four patients (77 %) achieved therapeutic anti-Xa levels in goal range during their hospitalization, with a mean enoxaparin dose of 0.71 mg/kg. Bleeding and thrombotic events were minimal and all patients that achieved an anti-Xa level in goal range did so with a dose less than 1 mg/kg of enoxaparin.