Pharmacokinetics of a Once-Daily Dose of Tacrolimus Early After Liver Transplantation: With Special Reference to CYP3A5 and ABCB1 Single Nucleotide Polymorphisms.

BACKGROUND The aim of the present study was to investigate the pharmacokinetics of the once-daily tacrolimus formulation (QD form) in relation to polymorphisms of the donor cytochrome P450 family 3 sub-family A polypeptide 5 (CYP3A5) gene and recipient adenosine triphosphate-binding cassette sub-family B member 1 (ABCB1) gene. MATERIAL AND METHODS A total of 80 consecutive living-donor liver transplant (LDLT) recipients were started on the QD form of tacrolimus (day 1), and 60 patients were completely followed for 7 days early after liver transplantation in order to evaluate the pharmacokinetics. RESULTS The concentration/dose (C/D) ratio in recipients with the donor CYP3A5 *1 allele was significantly lower throughout the observation period compared with those with the CYP3A5 genotype *3/*3 (p<0.001), while no effect of single-nucleotide polymorphisms (SNPs) of ABCB1 was observed. The administered doses required to achieve the target trough level were significantly higher on day 7 than on day 1 among all groups, regardless of the differences in the SNPs, especially among those with donor CYP3A5 *1 allele. The tacrolimus concentration was kept within the targeted level all through the study regardless of SNPs. CONCLUSIONS The donor CYP3A5 *1 allele correlated with the lower C/D ratio after administration of the QD form, and higher doses of QD-form tacrolimus and careful monitoring for the trough level should be considered, especially in recipients with the donor CYP3A5 *1 allele.