Antibodies specific for benzodiazepines were raised in rabbits by immunization with a conjugate of a benzodiazepine derivative, Ro 7#x2013;1986/1, with bovine serum albumin. The presence of anti-Ro 7#x2013;1986/1 antibodies in the sera was demonstrated by a radioimmunoassay using the radioligand 3Hflunitrazepam (3hFNZ). The antibodies displayed a high-affinity for 3HFNZ (KD= 0.073 #xB1; 0.003 nM) and cross-reacted with a broad spectrum of benzodiazepine derivatives. Benzodiazepine levels in samples of sera ana urine of benzoaiazepine-treated humans were determined. Due to the high sensitivity of the assay only minute volumes (microliter quantities) of body fluids are employed and, therefore, no extraction of the drugs is required. Nitrazepam and aiazepam levels as low as 20 picograms can be easily observed. Intoxicating levels of benzodiazepines can be detected by a single measurement in less than 10 min. This radioimmunoassay is advantageous for pharmacokinetic studies, toxicological examinations and forensic medicine due to its high sensitivity, wide-range specificity and technical simplicity.
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