Enoxaparin Dosing and AntiXa Monitoring in Specialty Populations: A Case Series of Renal-Impaired, Extremes of Body Weight, Pregnant, and Pediatric Patients.

The use of enoxaparin in specialty populations-including those with renal dysfunction, extremeness of body weight, pregnant patients, and pediatric patients-has not been studied in clinical trials. Monitoring anti-factor Xa activity (antiXa) as a surrogate to measure the activity of enoxaparin may be of interest. A case series of patients admitted to New York University Langone Health between December 2012 and July 2014 who received at least three consecutive doses of enoxaparin for the treatment of VTE and had a peak antiXa level drawn at steady state were evaluated. Patients were included if they were ≤ 18 years of age or if they were > 18 years of age and met one of the following criteria: pregnant, creatinine clearance (CrCl) ≤ 50 ml/min at the time of initiation of enoxaparin, or had a body weight ≤ 50 kg or ≥ 120 kg. A total of 31 patients were included in the analysis. The percentage of patients who achieved a therapeutic antiXa level (0.5-1.2 IU/mL for twice daily enoxaparin or 1-2 IU/mL for once daily enoxaparin) at the time of the first antiXa level drawn was greatest for the adult patients; however, the patients with renal impairment and low body weight were more likely to be sub-therapeutic at first antiXa level check. In addition, neonates and young children required increased enoxaparin doses to achieve therapeutic antiXa. Optimal dosing of enoxaparin in specialty populations has not been established. Furthermore, higher initial doses of enoxaparin may be needed in pediatric patients to attain therapeutic antiXa levels.