Tacrolimus concentrations
Once-daily tacrolimus was administered at 8 A.M., and the dose was adjusted according to the daily trough level of the drug (C0 or Cmin). The trough levels of tacrolimus were measured by liquid chromatography-tandem mass spectrometry using a Waters 2795 Alliance HT system (Waters Ltd., Watford, UK) and a Quattro micro API tandem mass spectrometer (Micromass, Manchester, UK). Before and after the conversion, all tacrolimus doses were adjusted according to the trough level of the drug, to obtain a therapeutic window of 2–8 ng/mL.