Neurotoxicity induced by tacrolimus after liver transplantation: Relation to genetic polymorphisms of the ABCB1 (MDR1) gene

Background. Tacrolimus is a substrate of P-glycoprotein (PGP) encoded by the multidrug resistant (MDR)1 gene (ABCB1). PGP, a multidrug efflux pump, restricts the distribution of tacrolimus in the brain. In this study, we investigate the correlation of ABCB1 gene polymorphism with tacrolimus-induced neurotoxicity in patients after liver transplantation. Methods. The genotype of 6 patients with neurotoxic events and 11 patients without neurotoxic events was analyzed by polymerase chain reaction (PCR), and 8 mutations were detected. In addition to laboratory findings and patient characteristics, the contribution of mutations in the ABCB1 gene was evaluated with stepwise discriminant function analysis. Results. High tacrolimus concentration, liver dysfunction, and mutation at position 2677 in exon 21 were demonstrated as positive predictors of tacrolimus-induced neurotoxicity. Conclusion. It is indicated that blood concentrations, liver function, graft weight, and polymorphism in the ABCB1 gene are important factors in tacrolimus-induced neurotoxicity.