Use of a monoclonal antibody for the therapeutic monitoring of cyclosporine in plasma and whole blood

The evaluation of a radioimmunoassay (RIA) for the monitoring of cyclosporine (CSA) that utilizes a monoclonal antibody specific for the parent compound is described. The assay exhibited good analytical recovery (greater than 95%), precision (coefficient of variation less than 10%), and linearity in plasma and whole blood specimens. The percentage cross reactivity of the major CSA metabolites M-17, M-1, and M-21 was less than 2%. The RIA gave values that were on average indistinguishable from those obtained by high-pressure liquid chromatography in plasma and whole blood specimens obtained from 49 renal transplant recipients.