Étude De La Variabilite pharmacocinetique Du Tacrolimus Chez Les TransplanteS Renaux.

Abstract

Kidney transplantation is the reference treatment for end-stage renal disease, offering a significant improvement in patient survival and quality of life. However, long-term graft success depends on optimal immunosuppression with tacrolimus, whose major inter- and intra-individual pharmacokinetic variability exposes patients to a dual risk: under-exposure leading to graft rejection, or over-exposure causing renal and neurological toxicity. Objective To analyse the genetic, clinical, demographic and ethnic determinants of tacrolimus pharmacokinetic variability, and to evaluate dose-individualisation strategies based on genotyping, the C₀/D ratio, intra-patient variability (IPV) and population pharmacokinetic models. Methods Qualitative literature review based on PubMed/MEDLINE, ScienceDirect, Cochrane Library and SpringerLink databases, integrating pharmacogenetic data (CYP3A5, CYP3A4, ABCB1, POR*28), international guidelines and population pharmacokinetic models. Results The CYP3A5*3 polymorphism is the main genetic determinant: expressers exhibit a 160–305% increase in clearance, requiring 1.5 to 2 times higher doses, while non-expressers require a 30–50% dose reduction. The CYP3A4*22 variant, particularly prevalent in North African populations, independently reduces clearance. Among non-genetic factors, haematocrit, albumin and comedications significantly modulate exposure, notably omeprazole (+20%) and amlodipine. Monitoring based solely on trough concentration C₀ shows major limitations: discordance with AUC and poor predictive value for clinical events. A C₀/D ratio < 1.05 emerges as a robust metabolic marker, predictive of nephrotoxicity and graft loss (HR = 2.03; TOMATO study). High IPV doubles the risk of graft loss and increases the risk of acute rejection by 40% when combined with a low C₀/D ratio. Conclusion Integrating CYP3A5/CYP3A4 genotyping, the C₀/D ratio, IPV and Bayesian pharmacokinetic models represents an indispensable multimodal approach to optimise tacrolimus exposure and improve long-term renal graft outcomes.