Enoxaparin Thromboprophylaxis Dosing and Anti-Factor Xa Levels in Low-Weight Patients

Introduction Enoxaparin is a widely used anticoagulant to prevent venous thromboembolism (VTE). A fixed dose is recommended for VTE prophylaxis. However, fixed prophylactic doses of enoxaparin in low-weight patients may be close to the weight-based dosing recommended for VTE treatment. Objective To evaluate peak anti-factor Xa (aFXa) levels in low-weight patients receiving enoxaparin for VTE prophylaxis. Methods Retrospective cohort of adult patients weighing < 55 kg who were hospitalized at Loma Linda University Medical Center between January 2008 and February 2017. All patients received enoxaparin for VTE prophylaxis with a peak aFXa level drawn. The primary endpoint was the proportion of patients achieving peak aFXa levels within the goal range of 0.2-0.5 unit/ml. Results Of 35 patients receiving enoxaparin for VTE prophylaxis with an appropriately timed peak aFXa level, 74% achieved goal peak aFXa levels and the median daily dose of enoxaparin was 30 mg. The mean weight was approximately 44 kg. No significant correlations between aFXa level and body mass index or body weight were found. Conclusion A lower dose of enoxaparin may be reasonable in low-weight patients for VTE prophylaxis. There appears to be no safety concerns with reduced enoxaparin dosing in low-weight patients. More robust data are needed to confirm these findings.