Enzyme linked immunosorbent assay for dexamethasone in equine urine

A simple and sensitive competitive Enzyme Linked Immunosorbent Assay [ELISA] with a colorimetric end point has been developed for the measurement of dexamethasone in equine sample. Use of pre-mixed reagent of untreated sheep antiserum and donkey antisheep alkaline phoshatase-labelled second antibody enables analysis of 40 duplicate urine sample within 75 minutes. The assay has good precision [Sr less than 5% for within and between assay runs] and is sensitive [LOD equivalent to 173 ng ml-l of diluted equine sample]. The assay has been used to detect the drug in urine over 20 hours in urine from a race horse following intramuscular [i.m.] injection of 20 mg of dexamethasone sodium phosphate