Conversion from twice-daily to once-daily tacrolimus does not reduce intrapatient variability in tacrolimus exposure

Background: Intrapatient variability (IPV) in tacrolimus exposure is associated with renal allograft failure. The aim of this study was to investigate whether conversion from the twice-daily tacrolimus formulation (Tac-TD) to a once-daily formulation (Tac-OD) leads to a lower IPV in tacrolimus exposure. Methods: Two hundred forty-seven stable renal transplant recipients were converted from Tac-TD to Tac-OD (Advagraf) on a 1:1-mg total daily dose basis. After conversion, patients were followed for 12 months and tacrolimus predose whole-blood concentrations (C 0), serum creatinine, estimated glomerular filtration rate, and proteinuria were measured. These parameters were compared with those collected at all outpatient visits in the 12-month period (±3 months) before conversion (Tac-TD period). The IPV was calculated based on the dose-adjusted tacrolimus C 0. Results: The Tac-OD formulation provided an excellent graft survival (100%), a low acute rejection rate (0.8%), and good tolerability. Renal function remained stable: estimated glomerular filtration rate 48 (16-90) versus 46 (12-90) mL/min (P = 0.15) before and after conversion, respectively. After conversion to Tac-OD, mean C 0 was significantly lower, decreasing from 5.7 ± 1.5 to 5.0 ± 1.5 ng/mL, corresponding to a 12% reduction (P < 0.01). Both drugs had similar IPVs (Tac-TD: 17.3% ± 1.6% versus Tac-OD: 16.4% ± 1.6%, P = 0.31). Conclusions: Although conversion from Tac-TD to Tac-OD significantly reduces tacrolimus exposure as measured by C 0 and seems safe, it does not reduce IPV in tacrolimus exposure.