Benzodiazepine concentrations in sera determined by radioreceptor assay for therapeutic-dose recipients

Using a radioreceptor assay, the authors determined benzodiazepine concentrations in sera of the 168 subjects who had been taking one or more benzodiazepines daily without showing excessive or adverse effects. In most of the recipients (150 of 168, 89.3%) of the sleep-inducing, anxiolytic, sedative, or anticonvulsant benzodiazepines, the concentrations were below 500 ng/mL in diazepam equivalents. Only two recipients (1.2%) showed concentrations above 1,000 ng/mL. These data will be useful in managing benzodiazepine therapy and in determining a diagnosis of benzodiazepine overdose.