Immunosuppressant therapeutic drug monitoring and trough level stabilisation after paediatric liver or kidney transplantation.

Immunosuppressive therapy must be guided by therapeutic drug monitoring (TDM) in paediatric liver (LT) and kidney transplantation (KT) patients to prevent under- and overdosing, which have clinical consequences. The purpose of our study was to analyse TDM results in our institutions and evaluate factors associated with blood level stabilisation after LT and KT. Blood levels of immunosuppressants were measured by immunoassay analysis. We compared blood level stabilisation between LT and KT, and evaluated associated factors in a retrospective study in two Swiss university hospitals. Forty-six patients (27 LT [median age 1.0 y], 19 KT [15.1 y]) were included. During the first month after transplantation, 32.8% (LT) and 41.2% (KT) of tacrolimus, and 22.1% (KT) of ciclosporin trough levels (measured before the next dose) were within target. In KT, trough levels stabilised earlier for tacrolimus than for ciclosporin (p = 0.02). Intensive care and hospital discharge occurred earlier in KT patients (p <0.001). Living-donor LT was associated with an earlier intensive care discharge compared with deceased donor (5.5 vs 11 days, p = 0.02). Primary metabolic disease and graft/recipient weight-ratio ≥0.03 was associated with earlier tacrolimus level stabilisation (14 vs 18 days, p = 0.01 and 15 vs 22 days, p = 0.05, respectively). In KT, recipient age (≥15.1 years) and weight (≥39.4 kg) were associated with an earlier trough level stabilisation (both 13 days vs not reached, p <0.001), and age with earlier hospital discharge (10 vs 14 days, p = 0.02). Immunosuppressant trough levels were often outside the target range in the first month after LT and KT. Organ-specific factors were associated with trough stabilisation.