Aims: The aim of this study was to examine the glomerular filtration rate (GFR) and tubular function at three months after renal transplantation in two groups of patients receiving cyclosporine A associated with either sirolimus (SRL) (n = 18) or everolimus (RAD) (n = 12), two structurally similar immunosuppressant drugs.
Results: Donors' and recipients' characteristics and mean cyclosporine A trough levels were similar in the two groups. The mean sirolimus trough level was 12.01 +/- 1.6 ng/ml whereas the mean everolimus trough level was 4.23 +/- 0.36 ng/ml. GFR, equated by the clearance of inulin, was higher in RAD patients (64 +/- 4 ml. min- 1.1.73 m(-2)) than in SRL patients (49 +/- 4 ml.min(-1) .1.73 m(-2)) (p < 0.05). The significant difference in GFR between the groups was not affected by differences in mean arterial blood pressures, or by differences in daily prednisone dosages, cyclosporine trough levels, or SRL and RAD trough levels. Phosphatemia, renal phosphate threshold (TmPO4/ GFR ratio) and uric acid clearance were significantly lower in the SRL than in the RAD group, despite similar levels of parathyroid hormone. Finally, urinary acid excretion was significantly lower in the RAD group.
Conclusion: In conclusion, regarding nephrotoxicity, our preliminary data suggest that it seems to be preferable to combine cyclosporine with RAD rather than with sirolimus in renal transplant patients. However, long-term renal effects of this combination are still to be determined in a larger cohort.