Comparison of Mycophenolate Dosing Strategies in Pediatric Heart Transplant

Mycophenolic acid (MPA) is a common immunosuppressant used in children post-orthotopic heart transplant (OHT). Multiple MPA dosing strategies exist, with limited reports of comparisons between dosing strategies and patient outcomes.

We performed a retrospective review of heart transplant recipients ≤ 21 years from 2014 to 2022, comparing dose concordance and clinical outcomes of weight-based mycophenolate dosing (15 mg/kg/dose every 12 h) to body surface area (BSA)-based dosing (600 mg/m²/dose every 12 h).

We analyzed 109 patients total (56% in the BSA-based cohort and 44% in the weight-based cohort). The BSA-based cohort received a higher total milligram dose (480 (IQR 200-563) vs. 636 (IQR 320-1000), p = 0.005), mg/kg dose (14.5 (IQR 13.7-16.1) vs. 20.7 (IQR 16.4-25.8), p < 0.001) and mg/m² dose (382 (IQR 333-470) vs. 596 (IQR 572-612), p < 0.001) compared to the weight-based cohort. The BSA-based cohort experienced a lower hazard of rejection (HR 0.2, 95% CI 0.1-0.4 vs. weight-based) and a greater hazard for overall infection (HR 2.2, 95% CI 1.2-3.9). There was no significant difference in 1-year post-transplant mortality and incidence of post-transplant lymphoproliferative disorder (PTLD).

This study demonstrates the discordance between two common mycophenolate dosing strategies (1200 mg/m²/day vs. 30 mg/kg/day) and its resultant impact on pediatric heart transplant-related outcomes. Further multicenter data would be useful to elucidate the impact on post-heart transplant morbidity and mortality.