An Evaluation of the Appropriateness of Initial Enoxaparin Dosing Among Pediatric Patients

Background Enoxaparin is a low molecular weight heparin that irreversibly inactivates factor Xa leading to the inhibition of clot formation. Despite the non-FDA approval in pediatrics, enoxaparin is recommended with an initial dose of 1.5mg/kg/q12hrs for patients aged ≤ 2 months and 1mg/kg/q12hrs for patients > 2 months, targeting therapeutic anti-Xa with a range of 0.5 to 1 units/mL. Due to more rapid clearance in pediatrics, our study aims to assess the need for initial higher doses than recommended by the guideline to reach the target anti-Xa level. Methods A retrospective chart review of all pediatric patients under all specialties who were treated with enoxaparin either in inpatient or outpatient settings between February 2021 and June 2022 at children's specialized hospital and meet the inclusion criteria, including age ≤ 15 years old and treated with enoxaparin with initial dose according to the American College of Chest Physicians (CHEST) guideline, while patients who received prophylaxis doses did not have anti-Xa levels or creatinine clearance < 30 mL/min/1.73m² were excluded. Demographic data, laboratory data, and enoxaparin dosing were all collected to assess whether the initial enoxaparin dose will result in a therapeutic level as a primary endpoint and secondary endpoints including the average enoxaparin dose required to achieve the therapeutic level and to report any side effects. All data were entered and analyzed using the Statistical Package for the Social Sciences (IBM SPSS Statistics for Windows, IBM Corp., Version 25, Armonk, NY), and all categorical variables were reported as frequency and percentage while continuous variables expressed as mean ± SD and the study was approved by our research center institutional review board (IRB). Results Thirty patients were included in the study (17 males), 10 patients were aged ≤ 2 months, four were between 3 and 12 months and 16 were > 12 months, most of the patients received enoxaparin for deep vein thrombosis. In the majority of patients (76.7%), the initial dose failed to achieve the target anti-Xa while a mean dose of 2 mg/kg/q12hrs in patients ≤ 2 months, 1.7mg/kg/q12hrs in patients 3-12 months and 1.3 mg/kg/q12hrs in patients > 12 months was sufficient to reach the target level. After achieving a therapeutic anti-Xa level, only one patient experienced major bleeding while four patients experienced minor bleeding, no edema or thrombocytopenia were reported. Conclusion In conclusion, initiating enoxaparin according to the recommended dose by the guideline failed to achieve target anti-Xa in the majority of patients which necessitates starting enoxaparin with initial higher doses according to the patient's age to provide more prompt achievement of target anti-Xa.