Body surface area-based dosing of infliximab is superior to standard weight-based dosing in children with very early onset inflammatory bowel disease

Background and Aims: Children with very early onset inflammatory bowel disease (VEO-IBD) are uniquely at risk of inadequate infliximab (IFX) exposure. We studied the association between standard body weight (BW)-based and body surface area (BSA)-based dosing strategies and outcomes. Methods: We identified VEO-IBD patients treated with IFX before 9 years at a single center. Patients were separated into those that received a BSA-based dose (200 mg/m2) and standard BW dosing (5 mg/kg). IFX drug levels, dose intensification, time on steroids, and long-term outcomes were compared. Receiver operator characteristic curves determined the optimal BW- and BSA-based dose to achieve a trough ≥10 μg/ml at dose 4 (IFX#4). Results: Forty-three children with VEO-IBD were identified. Receiver operator characteristic curves demonstrated optimal BW- and BSA-based doses to achieve IFX trough ≥10 μg/ml at IFX#4 were 7.5 mg/kg and 180mg/m2. Children were classified to standard BW dosing (22/43) and BSA dosing (10/43). IFX#4 trough was significantly higher in those who received BSA dosing (BSA 18.6 μg/ml [interquartile range 10.8–28.1] vs BW 5.1 μg/ml [interquartile range 2.6–10.7], P = .04). BSA dosing was more likely to achieve a target drug level >10 μg/ml at IFX#4 (BSA 70% vs BW 18%, P = .02). BW dosing was associated with a greater likelihood of dose escalation (BW 82% vs BSA 30%, P < .01) and a shorter time to first escalation. BSA dosing was associated with shorter time spent on steroids (P = .02). Conclusion: Young children require higher IFX dosing to achieve adequate drug exposure. Our data support the use of a BSA-based dose of 200 mg/m2 or, if a BW-based approach is used, 7.5 mg/kg. BSA dosing allows the use of a consistent dose over the age and weight spectrum.