Evaluation of Enoxaparin Dosing and Monitoring in Pediatric Patients at Children's Teaching Hospital

Abstract

OBJECTIVES: The primary objective of this study was to evaluate whether empirical enoxaparin doses according to Chest guidelines resulted in therapeutic antifactor Xa concentrations in pediatric patients. Secondary objectives were to determine the median enoxaparin dose that resulted in therapeutic anticoagulation, the median time to therapeutic concentrations, and the percentage of patients who experienced major bleeding. METHODS: Patients in a tertiary medical center who were <18 years of age and received treatment doses of enoxaparin between July 2007 and June 2010 were included. Patients with <2 antifactor Xa concentrations or with only supratherapeutic concentrations and doses that were higher than recommended by the guidelines were excluded. Subgroup analysis was conducted by dividing children into 4 age groups: <2 months of age, 2 months to <1 year of age, 1 year to <3 years of age, and 3 to 17 years of age. RESULTS: Thirty-two patients were included in the study. Thirty-seven percent of the patients achieved a therapeutic drug level with empirical dosing. The therapeutic dose ranged from 1 to 1.9 mg/kg in patients <1 year old, and 0.6 to 1.5 mg/kg in those =1 year of age. Comparison of the median therapeutic doses for patients 2 months to <1 year to that for patients =1 year old using the Mann-Whitney U test showed the median doses to be significantly difierent between the 2 groups (p=0.01). The antifactor Xa level became therapeutic on day 5 (median). There were no major bleeding events. CONCLUSION: Less than 40% of patients were therapeutic with empirical dosing, which supports findings from other studies that suggest a need for modification of empirical treatment dosing of enoxaparin in children.

Enoxaparin Dose Requirements to Achieve Therapeutic Low–molecular-weight Heparin Anti-factor Xa Levels in Infants and Young Children

“…However, bleeding events may have occurred outside of this time frame and may have been missed if they did not result in a hemoglobin decrease of >2 mg/dL or red blood cell or platelet transfusion, or if they were not documented in daily progress notes. Similar studies have identified major bleeding events in 0% to 2.6% of infants and children receiving enoxaparin for the treatment of thrombosis 6,8,9. The lack of identification of major bleeding events in our population within 1 week of therapeutic attainment supports the safety of enoxaparin in the treatment of thrombosis in infants and children even when doses are escalated above 1 mg/kg SQ every 12 hours.…”

“…Our results are consistent with previous retrospective studies of a similar design and with similar populations. McCormick and colleagues found that infants 60 days to 1 year of age required median enoxaparin doses of 1.5, 1.35, and 1.37 mg/kg, respectively 6,8,10. The number of infants between 60 days and 1 year of age in these studies ranged from 10 to 30 patients.…”

“…McCormick and colleagues found that infants 60 days to 1 year of age required median enoxaparin doses of 1.5, 1.35, and 1.37 mg/kg, respectively. 6,8,10 The number of infants between 60 days and 1 year of age in these studies ranged from 10 to 30 patients. This study is unique given the large cohort of infants included, which provided the opportunity to evaluate enoxaparin dose requirements in 2-month intervals throughout infancy.…”

“…These studies found that enoxaparin doses needed to achieve an anti-factor Xa level of 0.5 to 1 U/mL in infants were 1.3 to 1.6 times higher than the initial dose of 1 mg/kg subcutaneously (SQ) every 12 hours that is recommended by the ACCP guidelines. [6][7][8][9][10] Each of these studies showed a dose requirement inversely related to age wherein infants and young children required higher enoxaparin doses to achieve goal anti-factor Xa levels compared with older children.…”

Intravenous Enoxaparin in Pediatric Burn Patients: A Case Series

“…Although there are multiple studies and data that support enoxaparin dosing for VTE prophylaxis and treatment, as summarized by the CHEST guidelines, questions still remain on how the hypermetabolic state of burn patients affects medication dosing. McCormick et al 8 suggest that the standard dosing set forth by CHEST provides inadequate anti-Xa concentrations. With respect to the pediatric population, Brown et al 2 prospectively evaluated 35 pediatric burn patients to determine if 0.5 mg/kg of SC enoxaparin, dosed twice daily, would result in anti-Xa concentrations between 0.2 and 0.4 units/mL.…”