Cyclosporin-A (cy-A) is used for an immunosuppressant, but its narrow therapeutic index of effective concentration requires careful blood level monitoring of cy-A. Recently fluorescence polarization immunoassay (FPIA) of cy-A detection system in human serum level was commercialized, we compared FPIA with radioimmunoassay (RIA) and high performance liquid chromatography (HPLC) method. The correlation coefficient was r=0.873 between FPIA and HPLC in 62 serum samples of renal transplantation patients. FPIA system detected cy-A metabolite like peaks which fractionized by HPLC analysis. Further cyclosporin-D of HPLC internal standard substance was assayed in cy-A at 80% concentration.
With respect to these results, it was indicated that the FPIA caused to cross reactivity against to cy-A derivatives because of its polyclonal antibody use, and it made the determained value by FPIA greater than that by HPLC. However, it is a relatively simple and rapid procedure, this assay system is useful to facilitate the analysis of a large number of samples and to decide the sufficient dosage of cy-A after organ transplanted patient.