Detection of Dextromethorphan by RIA , as Expressed in Morphine Equivalents ( ME ) , In the Urines of Four Volunteers Receiving Daily Oral Doses of “ Romilar CF ” Cough Syrup

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 zg/liter and apparent serum concentrations of less than 10 .tg/liter. Patients receiving as much as 100 mg of methadone gave results (expressed as morphine) of less than 25 or 10 sg/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 ig of morphine per liter; 32 of 37 sera obtained up to 12 h after heroin contained more than 10 pg/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. Spector and Parker (1) have described a highly sensitive radioimmunoassay (RIA)’ for the detection of morphine and morphine-like compounds, in which use is made of rabbit antisera and [7,8-3H]dihydromorphine according to the Farr Technique (2), More recently, Van Vunakis et al. (3) described a radioimmunoassay for morphine that involves either rabbit or guinea pig antisera to morphine, morphine conjugate labeled with 125J and precipitation with specific antiglobulin serum. Other immunoassays are currently being used to identify and estimate morphine and morphine-like substances in urine and (or) serum (4-6, 11). Radioimmunoassays in general, including the two mentioned above, are not generally applicable to large-scale testing of human biological fluids because of the time required for assay and the complexity of the techniques. We describe here a rapid, simple radioimmunoassay for morphine and morphine-like substances and demonstrate the applicability of the method to the detection of these substances in urine and serum specimens obtained from known chronic heroin addicts. The test system used is a modification of the assay originally described by Spector and Parker (1).