Analysis of Tacrolimus Clearance in Patients with Kidney Transplants from Romania

<b>Background/Objectives</b>: Tacrolimus is a key immunosuppressant in kidney transplantation, but its high interindividual pharmacokinetic variability complicates dosing. This study aimed to develop a population pharmacokinetic model and identify the factors explaining variability to optimize tacrolimus therapy in Romanian kidney transplant recipients. <b>Methods</b>: The study included 106 kidney transplant recipients treated at Fundeni Clinical Institute (2022-2024). Tacrolimus blood levels were measured using immunoassays, while gene polymorphisms of CYP3A4, CYP3A5, and ABCB1 were identified by real-time polymerase chain reaction. <b>Results</b>: Patients with CYP3A4*1/*1.001 impact clearance (RSE = 11.8%), while hematocrit was a significant covariate for intercompartmental clearance (RSE = 6.14%). <b>Conclusions</b>: Incorporating CYP3A4*1/*1.001 genotype and hematocrit into dosing strategies can improve therapeutic drug monitoring and personalize immunosuppressive therapy.