A sensitive radioimmunoassay, incorporating solid-phase extraction, for fluticasone 17-propionate in plasma

Antibodies were produced in rabbits immunized with fluticasone 17-propionate (FP) conjugated to bovine thyroglobulin via its 3-carboxymethoxime with isobutylchloroformate. The antibodies were used to develop a sensitive and specific radioimmunoassay (RIA) for FP in human plasma. The limit of quantitation of the RIA is 50 pg per assay tube. This translates to 50 pg ml −1 plasma when a solid-phase extraction preceded the RIA. The interassay and intraassay relative standard deviations were