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Abstract

Introduction: Obesity is an independent risk factor for venous thromboembolism (VTE) and a major cause of morbidity and mortality. The optimal enoxaparin dosing for VTE prophylaxis in obese patients based on Anti-Xa levels and correlation of Anti-Xa levels with clinical outcomes remains controversial. Methods: Data were collected retrospectively on 139 adult obese patients (BMI ≥ 30 kg/m2) who received enoxaparin for VTE prophylaxis with at least one appropriately timed Anti-Xa level (drawn 3-5 hours after the third dose) from February 1, 2011 through August 31, 2012. Data were analyzed using appropriate descriptive statistics. Results: The mean BMI and weight were 38.3 kg/m2 (range 30.1 - 66.4) and 116.1 kg (range 70 - 208.7), respectively. The initial mean Anti-Xa level was 0.13 IU/mL (range 0 - 0.47) and 21.6% of patients initially achieved the target peak Anti-Xa level between 0.2 and 0.5 IU/mL. The initial mean enoxaparin dose was 0.56 mg/kg/day (range 0.19 - 0.96). The overall rate of bleeding was 23.7%, but only two patients discontinued enoxaparin due to concern for bleeding. Two VTE events were detected. Conclusions: Standard dosing of enoxaparin for VTE prophylaxis in obese patients is inadequate to achieve target peak Anti-Xa levels. Although a relatively low incidence of bleeding and VTE was observed, the correlation between Anti-Xa levels and clinical outcomes remains unclear. Further studies are needed to elucidate this relationship and to develop an algorithm for enoxaparin VTE prophylactic dosing in obese patients.