Tacrolimus population pharmacokinetics according to CYP3A5 genotype and clinical factors in Chinese adult kidney transplant recipients.

WHAT IS KNOWN AND OBJECTIVES

Tacrolimus is characterized by a narrow therapeutic index and a considerable inter- and intraindividual pharmacokinetic variability. The aim of our study was to develop a population pharmacokinetic model of tacrolimus in adult kidney transplant of Chinese patients, identify factors especially CYP3A5*3 genetic polymorphism that explain variability, and determine dosage regimens.

METHODS

Pharmacogenomic data obtained from 83 Chinese kidney transplant patients treated with tacrolimus were determined using polymerase chain reaction-restriction fragment length polymorphism analysis. Trough blood concentration data were collected from all of the patients during the 12 months of post-transplantation days and were analysed using the nonlinear mixed-effects modelling program. After building the final model, 1000 bootstraps were performed to validate the final model.

RESULTS AND DISCUSSION

A one-compartment model with first-order absorption and elimination adequately described the pharmacokinetics of tacrolimus. In this study, we observed that POD, HCT and CYP3A53 genotype were determinant factors in CL/F and POD related with V/F of tacrolimus significantly. The final model with the clearance covariates was presented as: Cl/F=THETA(1)EXP(THETA(4)(83/POD))(39.1/HCT)**THETA(5)*EXP(THETA(6)*CYP3A5), and the final model with the volume covariates was presented as: Vd/F=THETA(2)*POD**THETA(3). The Ka was fixed to 4.5 h .

WHAT IS NEW AND CONCLUSION

The HCT, CYP3A5*3 genetic polymorphism and POD contributed to the interindividual variability of oral tacrolimus in Chinese adult renal transplant patients.