Evaluation of Initial Enoxaparin Dosing and Antifactor Xa Levels in Infants Admitted to the Neonatal Intensive Care Unit

Introduction: Infants are at risk for thrombotic conditions due to multiple risk factors such as congenital heart defects and sepsis. According to the American College of Chest Physicians (ACCP) 2012 guidelines, enoxaparin may be given for thrombotic conditions at a dose of 1.5 mg/kg/dose every 12 h for patients less than 2 months of age and 1 mg/kg/dose every 12 h for those older than 2 months. Several studies have reported that infants typically require a higher initial dose of enoxaparin to reach therapeutic antifactor Xa levels than what is currently recommended. Methods: This is a single-center retrospective case-control study of hospitalized infants less than 12 months of age who received treatment with enoxaparin while admitted to the neonatal intensive care unit (NICU) at a freestanding children’s hospital. The primary objective was the difference between the initial enoxaparin dose (mg/kg) compared to the enoxaparin dose in which the patient first achieved a therapeutic antifactor Xa level of 0.5–1.0 units/mL. Results: A total of 56 infants were included in this study. The median enoxaparin dose at initiation was 1.5 mg/kg/dose, and the median enoxaparin dose at the first therapeutic antifactor Xa level was 1.9 mg/kg/dose (z = −12.7, p < 0.0001). There was no correlation between gestational age and weight with the enoxaparin dose required to reach a therapeutic antifactor Xa level. Conclusion: Infants admitted to the NICU, specifically those less than 4 months of age, require higher initial enoxaparin dosing to reach therapeutic antifactor Xa levels than what is currently recommended.