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Published on: October 12, 2012
Enoxaparin Population Pharmacokinetics in the First Year of Life
Brady S Moffett1, Marianne Galati, Donald Mahoney
1*Department of Pharmacy, Texas Children's Hospital; †Department of Pediatrics, Baylor College of Medicine; ‡The Texas Medical Center Library; and §Department of Pathology and Transfusion Medicine, Baylor College of Medicine, Houston, Texas.
Insights
Enoxaparin dosing in infants is variable. Postmenstrual age (PMA) incorporation into dosing regimens can reduce variability in enoxaparin pharmacokinetics for neonates and infants.
Area of Science:
- Pharmacology
- Pediatrics
- Drug Dosing
Background:
- Enoxaparin dosing in infants under one year is highly variable.
- Pharmacokinetic characterization is crucial for optimizing enoxaparin therapy in this population.
Purpose of the Study:
- To characterize enoxaparin pharmacokinetics in infants.
- To identify factors influencing enoxaparin dosing variability in neonates and infants.
- To inform optimized enoxaparin dosing strategies for pediatric patients.
Main Methods:
- Population pharmacokinetic analysis using NONMEM.
- Included 182 infants under 1 year postnatal age receiving enoxaparin.
- Excluded patients on renal replacement therapy or with hyperbilirubinemia.
Main Results:
- A 1-compartment model best fit the data.
- Allometrically scaled weight, serum creatinine, and postmenstrual age (PMA) influenced pharmacokinetic parameters.
- Dosing based on PMA showed less variability than postnatal age-based dosing.
Conclusions:
- Enoxaparin dosing in infants requires careful consideration of pharmacokinetic variability.
- Incorporating postmenstrual age (PMA) into enoxaparin dosing may improve therapeutic outcomes in infants.
Aims:
Enoxaparin dosing requirements in the first year of life can be highly variable. Characterization of pharmacokinetics in this patient population can assist in dosing.
Methods:
Patients less than 1 year postnatal age who received enoxaparin and had an anti-factor Xa activity level drawn as inpatients were identified through the pharmacy database over a 5-year period. Patients on renal replacement therapy or with hyperbilirubinemia were excluded. Data collection included demographic variables, indication for enoxaparin, enoxaparin doses, anti-factor Xa activity levels, serum creatinine, hemoglobin, hematocrit, platelet count, and urine output over the previous 24 hours. Population pharmacokinetic analysis was performed with NONMEM.
Results:
A total of 182 patients [male 50%, median 100 days postnatal age (range: 4-353 days)] met the study criteria. Patients received median 22 doses (range: 1-526) at a mean starting dose of 1.38 ± 0.43 mg/kg with median 5 (range: 1-56) anti-factor Xa activity levels measured. A 1-compartment proportional and additive error model best fits the data. Allometrically scaled weight significantly decreased the objective function value, as did serum creatinine on clearance, and postmenstrual age (PMA) on volume of distribution. When evaluated graphically, dosing based on PMA appeared to have less variability as compared to postnatal age-based dosing.
Conclusions:
Dosing of enoxaparin in infants younger than 1 year should incorporate PMA.
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