To describe the off-label use of antithrombin concentrate in tertiary care pediatric hospitals across the US.

This is a retrospective, multicenter, cohort study of 4210 admissions of children younger than 18 years of age who received antithrombin concentrate between 2002 and 2011 within the Pediatric Health Information System administrative database. An on-label admission was defined as an admission with an International Classification of Diseases diagnostic code for a primary hypercoagulable state; admissions without this code were classified as off-label.

During the 10-year study period, off-label use of antithrombin concentrate increased 5-fold. Overall, 97% of study subjects received antithrombin off-label. Neonates younger than 30 days of age comprised the largest age group (45.7%) of use; 87% of patients had at least one complex chronic condition, with congenital heart/lung defects being the most prevalent primary diagnosis (36.3%). Extracorporeal membrane oxygenation was the most common procedure associated with antithrombin use (43.7%).

The off-label use of antithrombin concentrate is increasing rapidly, particularly in critically ill children receiving extracorporeal membrane oxygenation, with few parallel studies to substantiate its safety or efficacy. Further preclinical and controlled clinical studies are critical to expanding our knowledge of this drug. In the meantime, antithrombin concentrate should be used judiciously by clinicians and following guidelines instated by hospitals.