[The development of mass-screening method for benzodiazepines by radioimmunoassay]

For the mass-screening of benzodiazepines in urine, radioimmunoassays (RIAs) for two benzophenones (metabolites of the drugs) were established, and an animal experiment was carried out to verify their usefulness. Immunogens were prepared by condensing 2-hemisuccinyl derivatives of 2-amino-5-chlorobenzophenone (A-CBP) or 2-amino-5-nitrobenzophenone (A-NBP) to bovine serum albumin (BSA). Antisera were produced in rabbits by immunization with the individual antigens. Two kinds of RIA were established separately for A-CBP and A-NBP using each antiserum, and their sensitivities were 150 pg/tube and 30 pg/tube, respectively. The antisera had broad cross-reactivity with many chlorbenzophenone and nitrobenzophenone derivatives, respectively. Diazepam or nitrazepam was administered to rats, and the total amounts of each in urine (benzodiazepines plus their metabolites such as benzophenones) were determined relative to time using the RIAs after acid hydrolysis of the specimen. The benzophenones were positive in urine even 9 h after administration, whereas diazepam was undetectable using a RIA against diazepam. The characterization of the antisera and the results of the animal experiments indicate that these RIAs will be very useful for mass-screening of benzodiazepines.