Urinary Screening for Benzodiazepines with Radioreceptor Assay: Comparison with EMIT® d.a.u. Benzodiazepine Assay and High-Performance Liquid Chromatography

The radioreceptor assay (RRA) provides a total estimate of all pharmacologically active forms of benzodiazepines and their metabolites. We evaluated the method for urine drug screening. Detection limits of the most commonly used benzodiazepines and their major metabolites were determined. In all cases, the detection limits were lower than the cutoff values specified for the Syva EMIT d.a.u. benzodiazepine assay. Thirty-three urine samples for routine drug screening were tested for benzodiazepines by RRA and EMIT. Results were compared with those obtained by a highly specific high-performance liquid chromatographic (HPLC) method. Five commonly used benzodiazepines and their major metabolites were identified by use of a computerized multichannel photodetector. We obtained two false-negative results by RRA when compared with HPLC. These may be caused by conjugate formation. The inclusion of a simple enzymatic hydrolysis improves the detection of compounds excreted in the urine as glucuronide conjugates (e.g., oxazepam). We conclude that the combination of enzymatic hydrolysis and direct RRA provides a rapid and acceptable method for detection of the presence of benzodiazepines in urine samples.