Clinical Chemistry, Vol 21, 1378-1382, Copyright © 1975 by the American Association for Clinical Chemistry

Simultaneous Detection of Morphine and Barbiturates in Urine by Radioimmunoassay

¹ Department of Diagnostic Research, Hoffmann-La Roche Inc., Nutley, N. J. 07110.

This report describes a radioimmunoassay for the simultaneous detection of morphine and barbiturates. Morphine and barbiturate antibodies, obtained from goats, were mixed with ¹²⁵I-labeled antigens. By adjusting concentrations of the morphine and barbiturate antibodies and radiolabeled antigens, closely superimposed standard curves for the two drugs would be obtained. As a consequence, similar response curves were obtained for urine specimens containing morphine or barbiturates. Although concentrations as low as 25 µg/liter could be measured, to ensure against false positive reactions the test should be performed at the 100 µg/liter concentration. Unknown samples positive by the dual assay were confirmed by separately testing the specimens with the individual radioimmunoassay specific for morphine or barbiturate. Equivalency tests of urines positive for morphine, positive for barbiturates, or negative for both demonstrated complete correlation between the single and dual assays. The mixed reagent retained its sensitivity and specificity for at least three months when stored at 4 or 25 °C. The dual radioimmunoassay is a rapid, simple procedure that can be adapted to automated processes and that is suitable for largeand small-scale screening.

Submitted on October 10, 1974
Accepted on June 4, 1975