Population pharmacokinetics of tacrolimus in kidney transplant patients

The purpose of this study was to derive population pharmacokinetics (PPK) model of tacrolimus clearance, identify and describe factors that influence it in Serbian kidney transplant patients.

Population pharmacokinetics analysis was performed using nonlinear mixed-effects model (NONMEM) program from Serbian adult kidney transplant patients receiving triple immunosuppressive therapy, including oral tacrolimus. Details of drug dosage history, sampling time and tacrolimus concentration in 63 patients (44 males and 19 females), 27 - 57 years old (age mean 40.88 +/- 7.01 years) were collected retrospectively. Effects of several covariates on tacrolimus clearance were tested: total body weight, gender, age, posttransplantation days, hemoglobin count, CRP, alanine aminotransferase/aspartate aminotransferase, total daily dose of tacrolimus, co-medication with cotrimoxasole, omeprazole, mycophenolate mofetil and prednisone (> 25 mg).

Typical mean value of tacrolimus clearance, estimated by the base model (without covariates), in our population was 1.03 l h-1. The final model showed that tacrolimus clearance increased with total daily dose and concomitant administration of high-dose prednisone (> 25 mg). The magnitude of prednisone effect was + 1.16 l h-1. Final model was validated in a group of 17 patients, showing good predictive performance.

The derived model describes well tacrolimus clearance in terms of characteristics of Serbian kidney transplant patients, offering basis for rational individualization of tacrolimus dosing regimens.