Immunological screening of benzodiazepines in urine: improved detection of oxazepam intake.

Immunological screening analysis of benzodiazepines in urine using the EMIT (enzyme multipled immuno-technique) and FPIA (fluorescence polarization immunoassay) techniques does not reliably detect the intake of therapeutic doses of oxazepam. In 23 patient urine samples, in which the presence of oxazepam could be verified chromatographically, only about 50% were detected as positive in the immunoassay systems. However, when the screening procedure was modified to include a simple step of hydrolysis of urine using the enzyme beta-glucuronidase to liberate conjugated oxazepam, improved detection of oxazepam intake was achieved. With EMIT 95% and with FPIA 100% of the samples were detected as positive. Since oxazepam arises in vivo also as a metabolite of other common benzodiazepines, the modification will most likely contribute to the generally improved detection of benzodiazepines.