Homogeneous Enzyme Immunoassay for Opiates in Urine

Abstract

Abstract An assay technique, homogeneous enzyme immunoassay, is described for the quantitative determination of morphine derivatives in biological fluids. An enzyme is labeled with morphine. When the enzyme-labeled morphine is bound by antimorphine antibodies, the enzyme is rendered inactive. Free morphine competes with enzyme—morphine for antibody binding sites preventing inhibition of enzyme activity. Enzyme activity is thus directly related to the concentration of free morphine. See PDF for Equation Where the enzyme used is lysozyme, the assay can detect 0.5 µg of morphine per milliliter of urine with >95% confidence (CV, 5.0% at 0.5 µg/ml morphine). The technique gave nearly twice as many confirmed positives as did thin-layer chromatography in a comparative study of urines from a methadone maintenance program. The immediacy of the results (assay time: <1 min) permits use of the assay in hospital emergency rooms, law-enforcement facilities, and methadone treatment programs.