A comparison of five commercial immunoassays for the detection of flunitrazepam and other benzodiazepines in urine

Five commercially available immunoassay test kits (SYVA EMIT(R) d.a.u(TM), SYVA EMIT(R) II assay, Abbott FPLA, Cozart Auto-Lyte(R) and Roche Abuscreen (R) Online(TM), all used for the benzodiazepine group of drugs) were evalua ted for their ability to detect flunitrazepam, its major urinary metabolite , 7-aminoflunitrazepam, and several other benzodiazepines at serial dilutio ns (final concentration 25-1000 ng/ml) in drug-free urine and in urines fol lowing oral administration of flunitrazepam (1-3 mg). For comparison, gas c hromatography/mass spectrometry was used to measure urinary levels of 7-ami noflunitrazepam. Levels of drug detected in the study were compared with th e cross-reactivities presented by the manufacturers for each individual kit . One to three mg doses of flunitrazepam were taken by volunteers and level s excreted in urine analysed over several hours. A positive response was ob tained in several samples from volunteers who had taken 2 mg or 3 mg doses, but not a 1 mg dose. Thirty-five clinical samples from the individuals sus pected of benzodiazepine abuse were also examined. The results were not con sistent among the kits evaluated. We conclude that the test kits evaluated in this study do not detect flunitrazepam reliably due primarily to their p oor sensitivities.