Cyclosporine monitoring by fluorescence polarization immunoassay.

The monitoring of cyclosporine levels in whole blood and serum has become a routine procedure for the post-transplant management of immunosuppression. We have developed fluorescence polarization immunoassays for cyclosporine in whole blood and in serum using a monoclonal antibody. These assays are fast (20 determinations in less than 22 min), sensitive (25 micrograms/L for whole blood samples and 10 micrograms/L for serum samples), and precise (CV less than 7% in both assays). Cross-reactivities with AM1 (Metabolite 17) and AM4N (Metabolite 21) are less than 8.5 and 2.5%, respectively, for both assays.