The aim of this study is to evaluate the potential of endogenous cortisol and cortisone metabolism as a biomarker for immunosuppressive agents disposition in Chinese renal transplant recipients. If the blood concentrations of immunosuppressants can be predicted successfully, this new probe may take place of current drug monitoring post transplantation.

Immunosuppressive agents, including cyclosporine A, tacrolimus, and sirolimus, have been widely used to improve the outcome of organ transplantation. The need for frequent and specific monitoring of drug concentrations remains essential, since the therapeutic dosing and pharmacokinetics show great variability among recipients. However, this may be time and cost consuming. Indeed, cyclosporine A, tacrolimus, and sirolimus are all metabolized by CYP3A, consisting with the metabolic characteristic of endogenous cortisol and cortisone. Hence, the present study is designed to determine if the endogenous cortisol and cortisone metabolism can be used as an noninvasive probe for immunosuppressants pharmacokinetics in Chinese renal transplant recipients.

Inclusion Criteria:

• Chinese adult patients who had undergone their first renal transplantation； All patients received an immunosuppressive regimen containing immunosuppressive agents, mycophenolate mofetil, and corticosteroids; All patients had normal liver and renal function.

Exclusion Criteria:

• an acute rejection episode or infection; multiple organ transplantation; taking any other medications known to interact with immunosuppressive agents, with exception of calcium-channel blockers; abnormal findings on physical examination or laboratory tests.