A Sensitive, Rapid Radioimmunoassay for Morphine and Immunologically Related Substances in Urine and Serum

A rapid, simple radioimmunoassay for morphine and immunologically related compounds is described and evaluated. The 2-h assay requires as little as 0.1 ml of urine or serum and provides a quantitative estimate of serum or urinary morphine. Individuals known not to be receiving heroin or other narcotics had apparent urinary morphine concentrations of less than 25 µg/liter and apparent serum concentrations of less than 10 µg/liter. Patients receiving as much as 100 mg of methadone gave results (expressed as morphine) of less than 25 or 10 µg/liter, respectively, for their serum and urine. Fifty-eight of 59 urines from known heroin users, sampled up to 48 h after self-administered heroin, contained more than 25 µg of morphine per liter; 32 of 37 sera obtained up to 12 h after heroin contained more than 10 µg/liter. Samples obtained from individuals receiving substances that may cross-react in the assay were tested and the results are discussed. We conclude that this radioimmunoassay may be suitable for routine screening of urine or serum for morphine.