Abstract: Aim To monitor the whole blood trough concentration of cyclosporine A(CsA)in renal transplant recipients, and to suggest optimal therapeutic window of CsA. Methods CsA concentration in 3275 blood samples from 521 renal transplant recipients was measured by specific fluorescence polarization immunoassay. The whole blood trough CsA concentrations were compared according to different times after operation and clinical symptoms.Results The optimal therapeutic window of CsA should be 250～ 450 μg/L (less than 1 month after operation), 200～ 400 μg/L(1～ 3 months), 150～ 300 μg/L (3～ 6 months), 100～ 250 μg/L (6～ 12 months), 100～ 200 μ g/L(1～ 2 years), 100～ 180 μ g/L(more than 2 years), 100～ 180 μg/L(more than 2 years), respectivily. Conclusion The satistical analysis indicated that frequency of toxic effects and rejection reaction would significantly be reduced if CsA whole blood levels were adjusted to therapeutic and safe range.

Key words: cyclosporine A ;kidney/transplantation;therapeutic drug monitoring ; specific fluorescence polarization immunoassay