Detection of drugs of abuse by radioimmunoassay: a summary of published data and some new information

Abstract

A review is given of the status of radioimmunoassays for detection of abused drugs. Individual assays with use of 125I labeled antigens are all performed in an identical manner and can be completed in 30 min to 1 h. Combined assays for simultaneous detection of two or more such drugs or assays in which a tritium labeled antigen is used require 1-2 h for completion. All tests can be performed with 0.1 ml or less of specimen. The assays involving 125I reliably detect urinary concentrations of, per liter, 40-100 μg of morphine, 100 μg of barbiturates, methadone, methaqualone, or benzoylecgonine, and 1000 μg of amphetamine. The assay for morphine involving 3H detects 60 μg/liter. Each assay is capable of providing a qualitative and quantitative estimate of the drugs sought. The 125I labeled antigens have a usable shelf life of at least two to four months after the antigen is iodinated; the tritium assay is stable for six months. The assays can be performed with use of paper discs that have been suspended in urine and then dried, in place of the liquid specimen. The assays appear to be equally applicable to detection of drugs in urine, blood, saliva, and tissues. All of them are done at ambient temperature and can be used equally well for emergency (stat) tests or mass screening. Except for the benzoylecgonine assay, the clinical reliability of these tests has been demonstrated.