Determination of cyclosporine A in whole blood: Comparison of a chromatographic method with three different immunological methods

Cyclosporine A is potent immunosuppressive agent characterized by a narrow therapeutic range, inter- and intra-individual variability and a lack of correlation between drug dosage and blood levels. In view of these facts, blood levels of CyA should be routinely monitored to assess organ rejection and toxicity. luated CyA as well as its metabolites (AM9, AM19, AMl, and AM4N) in whole blood samples from 117 patients using commercially available immunological assays (AxSYM, EMIT, Dimension) and HPLC. reactivity of the immunological assays was evaluated using different concentrations of the CyA metabolites (in vitro cross-reactivity) and by statistical analysis of patient data (in vivo cross-reactivity). Cross-reactivity was seen in all immunological assays, with differences in in vitro and in vivo cross-reactivity. atistical analysis showed a classical correlation between HPLC and AxSYM of r2 = 0.89, HPLC versus EMIT of r2 = 0.93, and HPLC versus Dimension of r2 = 0.93. rcentage metabolite cross-reactivity (%) by immunological assays for four metabolites at two concentrations each (250 and 1000 ng ml−1) was lowest with the Dimension assay. immunological methods examined, the new Dimension for CyA determination can be relied on to produce results comparable to HPLC; other advantages are its simplicity, practicability and ease of handling.