Pharmacokinetic Profile of Twice- and Once-daily Tacrolimus in Pediatric Kidney Transplant Recipients

Background The aim of this study was to assess the differences in pharmacokinetic (PK) profiles after the 1:1 ratio-based conversion from a twice-daily to a once-daily tacrolimus formulation (TD-TAC and OD-TAC, respectively) in pediatric recipients of kidney transplants. Methods TD-TAC was initially administered to 29 pediatric patients who underwent kidney transplantations between April 2010 and September 2015 and were then subsequently switched to OD-TAC. The switch dose ratio was 1:1, and the 24-hour complete PK parameter assessment was performed before and after the regimen was changed from TD-TAC to OD-TAC. Results The mean total daily dose at baseline was 5.5 ± 2.9 mg (0.18 ± 0.10 mg/kg body weight). Consecutive PK studies revealed no significant difference in the mean time to achieve maximum concentrations and the area under the concentration–time curve from 0 to 24 hours (AUC 0–24 ) of both drug formulations. However, the mean trough concentration (C min ) and the maximum concentration of OD-TAC were 22% and 6% lower and higher, respectively, than those of TD-TAC. Therefore, a better correlation was observed between the AUC 0–24 and C min of OD-TAC than between those of TD-TAC. Conclusions After the change from TD-TAC to OD-TAC, the AUC 0–24 values were equivalent despite a 22% reduction in C min . C min may therefore be an excellent predictor in the therapeutic drug monitoring of OD-TAC because of its superior correlation with AUC 0–24 .