Interleukin-2 profiles shortly after tacrolimus conversion from a twice-daily to once-daily regimen

A number of studies have indicated that kidney recipients can be safely converted from the twice-daily formulation (Tac-T) to the same dose of a once-daily tacrolimus (TAC) regimen (Tac-O) based upon monitoring of renal function. Conversion from Tac-T to Tac-O is commonly followed by a reduction in Tac trough levels, estimated by some authors to be about 20%. These alterations seem to not be associated with a modification of graft function, but study of inflammatory cytokines would be useful. The aims of our study were to monitor Tac, C-reactive protein (CRP), and interleukin (IL)-2 levels as well as to evaluate renal function among stable renal transplant patients converted from a Tac-T to a Tac-O regimen. We enrolled 10 consecutive stable kidney transplanted patients. Tac trough levels, serum creatinine concentrations, glomerular filtration rates using the Modification of Diet in Renal Disease formula (MDRD), CRP, and clinical assessment were performed monthly for 6 months before and 3 months after the conversion. After conversion we observed a slight but not significant reduction in Tac trough level. Renal function evaluated by serum creatinine and MDRD as well as CRP were not significantly different after conversion. IL-2 levels remained stable after conversion. We identified a group of patients showing reduced Tac trough levels below the therapeutic range and a group with stable Tac levels. No significant differences were observed among the two groups before versus after the conversion. Our results did not show a modification of IL-2, CRP and renal function levels, at 3 months after conversion despite the lower Tac trough concentrations. The clinical meaning of Tac trough alterations is not clear. They might reflect inter- and intraindividual differences in the clearance of Tac as recently described. They did not seem to be associated with activation of an inflammatory pathway.