Rapid fluorescence enzyme-linked immunosorbent assay for dexamethasone in equine urine

Abstract

A simple and sensitive competitive ELISA with a fluorescent end-point has been developed for the measurement of dexamethasone in equine urine samples. Use of pre-mixed reagent of untreated sheep antiserum and alkaline phosphatase-labelled second antibody enables the analysis of 40 duplicate urine samples within 55 min. The assay has good precision (RSD less than 10% for within and between assay runs) and is reasonably sensitive (LOD equivalent to 174 ng ml^–1 of diluted equine sample). The assay has been used to detect the drug over 23 h in urine from a race horse following intramuscular injection of 20 mg of dexamethasone sodium phosphate.