Abstract
Calcineurin inhibitor nephrotoxicity remains an issue for transplant recipients. The pharmacokinetic profile (PK) of the once-daily tacrolimus extended release (Tac-ER) includes equivalent exposure [AUC(0-24 h) ] but lower Cmax versus twice-daily tacrolimus immediate release (Tac-IR). We hypothesized that the unique PK profiles would result in pharmacodynamic differences in renal function. Nineteen healthy male subjects were allocated to once-daily Tac-ER and twice-daily Tac-IR in a prospective, randomized, two period, cross-over study. Tacrolimus was titrated to achieve trough levels of 8-12 ng/ml. Twenty four hours ERPF and GFR estimated by para-aminohippurate and sinistrin clearance were performed at baseline and at the end of each 10-day dosing period. Mean Tac C0 was 11.0 ± 2.2 and 11.3 ± 1.8 ng/ml for Tac-ER and Tac-IR, respectively. The mean Effective 24 h renal plasma flow (ERPF) was significantly higher with Tac-ER compared with Tac-IR (658 ± 127 vs. 610 ± 93 ml/min/1.73 m(2) , P = 0.046). There was a trend to a greater mean GFR over 24 h for Tac-ER at 114.5 ± 13.6 ml/min/1.73 m(2) compared with 108.9 ± 9.7 ml/min/1.73 m(2) for Tac-IR, P = 0.116. Under controlled physiological conditions, ERPF was significantly improved with Tac-ER compared with Tac-IR, likely owing to the differing PKs of these tacrolimus preparations (ClinicalTrials.gov Identifier: NCT01681134).