Population pharmacokinetics and dosage optimization of tacrolimus in pediatric patients with nephrotic syndrome .

Objectives: The aims of this study were to investigate the population pharmacokinetic (PPK) characteristics of tacrolimus in Chinese children with nephrotic syndrome and to apply it in clinical practice.

Materials and methods: A total of 137 concentrations from 61 patients were collected from routine therapeutic drug monitoring data between 2011 and 2018. Population modeling was performed with the nonlinear mixed-effects model (NONMEM) program, using a one-compartment model with first-order absorption and elimination. The mean population estimate values of clearance (CL/F) and volume of distribution (V/F) were determined. Common demographic and clinical variables were tested for their influence on these parameters. External validation was conducted, and Monte Carlo simulation, based on the final model, was carried out to determine optimal dosage regimen.

Results: Age and body weight were the covariates that displayed a significant influence on CL/F and V/F according to the final regression model. Goodness-of-fit plots, bootstrap outcomes, and external validation confirmed the relatively good stability and prediction capability of the model. The interindividual variability of CL/F was 31.10%, and the residual variability was 0.91 ng/mL. Mean prediction error (MPE, %) and Mean absolute prediction error (MAPE, %) were 10.3% and 16.6%, respectively. Monte Carlo simulation based on the final model was carried out to determine optimal dosage regimen.

Conclusion: A PPK model of tacrolimus in children with nephrotic syndrome was developed. Age and bodyweight could partly explain the interindividual variability in the CL/F and V/F of tacrolimus. The final model could be used to accurately predict tacrolimus individual pharmacokinetic parameters and assist in dosage optimization.
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