Prednisolone pharmacokinetics after oral prednisone administration in paediatric patients with kidney transplant.

AIMS:Glucocorticoids are 1 of the primary treatments in paediatric kidney transplantation. The aims of this study were: (i) to build a population pharmacokinetics (PPK) model of free prednisolone, which is the active form of prednisone, in paediatric kidney transplant recipients; (ii) to identify covariates accounting for interindividual variability (IIV) of pharmacokinetics (PK) parameters; and (iii) to investigate drug exposure-safety relationships. METHODS:Ninety-seven samples were obtained from 39 paediatric kidney transplant recipients (aged 3.4-17.2 years) in order to investigate prednisone PPK. We selected children receiving oral prednisone as part of their immunosuppressive regimen. A PPK analysis was performed using Monolix. RESULTS:A 1-compartment model best described prednisolone concentrations. Large IIV was observed as prednisolone was undetectable at H12 in some patients but could still be detected at H24 in others. Both bodyweight and ciclosporin cotreatment influenced the PK. The clearance (CLU ) and volume of distribution of free prednisolone allometrically scaled to 70 kg were 27.6 L/h and 101 L. Ciclosporin cotreatment decreased CLU by 67%. High blood pressure and new onset diabetes after transplantation were associated with daily free prednisolone exposure. CONCLUSION:This study is the first analysis of prednisolone PPK in kidney-transplanted children. Some of the IIV in the PK parameters was explained by bodyweight and ciclosporin cotreatment. These data suggest that dose adjustment is required after identifying variability factors to optimize efficacy and limit side effects. The use of therapeutic drug monitoring in kidney-transplanted children may be useful, especially with respect to safety issues.