Enoxaparin is a commonly utilized anticoagulant, particularly in infants and children. Recent literature has highlighted the need to initiate enoxaparin at higher doses, especially at younger ages, due to differences in pharmacokinetics and pharmacodynamics. The aim of this study was to investigate the enoxaparin dose required to achieve therapeutic effect in patients ≤ 2 months, >2 to ≤ 6 months, >6 to ≤ 12 months, and >12 months old.

This retrospective chart review includes patients aged 0–18 years admitted to the cardiac ICU or cardiac stepdown unit over a five-year period. Patients were included who achieved a therapeutic anti-Xa within goal of 0.5–1 units/mL.

Seventy-one patients were included in the analysis; 26 (37%) were ≤ 2 months old, 21 (30%) were >2 to ≤ 6 months old, 10 (14%) were >6 to ≤12 months old, and 14 (20%) were >12 months old. There was a significant difference in the median enoxaparin dose required among these age groups, with medians of 2.13 mg/kg/dose [IQR: 1.95, 2.53], 1.81 mg/kg/dose [IQR: 1.52, 2.40], 1.44 mg/kg/dose [IQR: 1.31, 1.71], and 1.16 mg/kg/dose [IQR: 1.00, 1.26], respectively (p < 0.001). The difference between initial and therapeutic doses was greater in infants compared to children >12 months of age, despite higher initial doses in patients ≤ 6 months old.

Infants admitted to the cardiac ICU or cardiac stepdown unit required an increased median enoxaparin dose and a higher number of dosing changes and experienced longer times to achieve therapeutic anti-Xa levels compared to older children.