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Abstract
Five commercially available immunoassay test kits (SYVA EMIT(R) d.a. UTM, SYVA EMI II assay, Abbott FPIA, Cozart Auto-Lyte`R' and Roche Abuscreen( OnlineTM, all used for the benzodiazepine group of drugs) were evaluated for their ability to detect flunitrazepam, its major urinary metabolite, 7-aminoflunitrazepam, and several other benzodiazepines at serial dilutions (final concentration 25 100 ng/ml) in drug-free urine and in urines following oral administration of f It<nitrazepam (1-3 mg). For comparison, gas chromatographyl mass spectrometry was used to measure urinary levels of 7-aminoflunitrazepam. Levels of drug detected in the study were compared with the cross-reactivities presented by the manufacturers for each individual kit. One to three mg doses of flunitrazepam were taken by volunteers and levels excreted in urine analysed over several hours. A positive response was obtained in several samples from volunteers who had taken 2 mg or 3 mg doses, but not a I mg dose. Thirty-five clinical samples from the individuals suspected of benzodiazepine abuse were also examined. The results were not consistent among the kits evaluated. We conclude that the test kits evaluated in this study do not detect flunitrazepam reliably, due primarily to their poor sensitivities.
Introduction
Flunitrazepam (Rohypnol ) is a 7-nitro-1, 4-benzodiazepine derivative which possesses muscle relaxant properties as well as sedative effects. ' The drug is intermediate to long-acting with a variable terminal half-life of 10-70 hours (mean 25).2 While legally available in Central and South America, and in Europe, its use is not permitted in Canada and the United States. The use of flunitrazepam as an illicit drug is now a growing concern, often being used in combination with other drugs of abuse such as cocaine and heroin.3 The amount of flunitrazepam taken by those abusing it can be up to 20 times the recommended 1 mg dose. It has also been alleged to be involved in date rape where, in such instances, the drug has been dissolved in a drink, incapacitating the unsuspecting victim, leading to sexual assault.4 Analysis of flunitrazepam in urine is complicated by almost complete metabolism of the drug. It is metabolized by reduction of the nitro group to produce predominantly 7-aminolunitrazepam. Minor metabolites include 3-hydroxyflunitrazepam and lV-desmethylflunitrazepam.2
In general, benzodiazepines are screened for by immunoassay techniques. Samples...