Population pharmacokinetic models of tacrolimus in paediatric solid organ transplant recipients: A systematic review

Aims This study aimed to provide up‐to‐date information on paediatric population pharmacokinetic models of tacrolimus and to identify factors influencing tacrolimus pharmacokinetic variability. Methods Systematic searches in the Web of Science, PubMed, Scopus, Science Direct, Cochrane, EMBASE databases and reference lists of articles were conducted from inception to March 2023. All population pharmacokinetic studies of tacrolimus using nonlinear mixed‐effect modelling in paediatric solid organ transplant patients were included. Results Of the 21 studies reviewed, 62% developed from liver transplant recipients and 33% from kidney transplant recipients. Most studies used a 1‐compartment model to describe tacrolimus pharmacokinetics. Body weight was a significant predictor for tacrolimus volume of distribution (Vd/F). The estimated Vd/F for 1‐compartment models ranged from 20 to 1890 L, whereas the peripheral volume of distribution (Vp/F) for 2‐compartment models was between 290 and 1520 L. Body weight, days post‐transplant, CYP3A5 genotype or haematocrit were frequently reported as significant predictors of tacrolimus clearance. The estimated apparent clearance values range between 0.12 and 2.18 L/h/kg, with inter‐individual variability from 13.5 to 110.0%. Only 29% of the studies assessed the generalizability of the models with external validation. Conclusion This review highlights the potential factors, modelling approaches and validation methods that impact tacrolimus pharmacokinetics in a paediatric population. The clinician could predict tacrolimus clearance based on body weight, CYP3A5 genotype, days post‐transplant or haematocrit. Further research is required to determine the relationship between pharmacogenetics and tacrolimus pharmacodynamics in paediatric patients and confirm the applicability of nonlinear kinetics in this population.