Comparison of Anti-Xa Levels in Obese and Non-Obese Pediatric Patients Receiving Treatment Doses of Enoxaparin

Objective To determine if using actual body weight to dose enoxaparin in obese pediatric patients results in higher anti-Xa levels compared with non-obese pediatric patients. Study design This was a retrospective case-matched study of obese and non-obese pediatric patients receiving treatment doses ofenoxaparin in a tertiarycare children'shospital. Patientswere includedif theywere initiatedontreatment doses of enoxaparin, had appropriate anti-Xa levels drawn, and were between 2 and 18 years of age. Patients with renal insufficiency, hyperbilirubinemia, goal anti-Xa level <0.5 or >1 unit/mL, or receiving mechanical circulatory support were excluded. Obese patients whomet study criteria were matched on a 1:1 basis with non-obese patients. Results All baseline characteristics were similar except for body mass index percentile (98.2 +/- 2 vs 48.7 +/- 15, P < .01). Obese patients had higher initial anti-Xa levels (0.67 +/- 0.27 vs 0.53 +/- 0.24 unit/mL, P = .028). Over time, obese patients required a lower mean dose to achieve therapeutic anti-Xa levels than non-obese patients (0.81 +/- 0.19 vs 1.1 +/- 0.4 mg/kg, P = .005). Conclusions The mean initial anti-Xa level was higher in obese pediatric patients compared with non-obese pediatric patients, but a dosage adjustment was not required. Obese patients may need closer monitoring over time to avoid supratherapeutic levels and possible bleeding events. (J Pediatr 2013;162:293-6).