Application of radioreceptor assay of benzodiazepines for toxicology

A radioreceptor assay (RRA) for determining benzodiazepines (BZ) has been developed and applied to toxicological analysis of serum from 21 patients with acute BZ overdosage. The method was sensitive (e.g., lorazepam 17 nM, diazepam 41 nM), and specific for pharmacologically active BZ derivatives. The reproducibility of the results was good (intra-assay variation less than 8%, inter-assay variation less than 10%). Concentrations measured by the RRA showed a good correlation with those obtained by gas-liquid chromatographic analysis of the same samples. The quantitative results represent the sum of one or several parent substances and all biologically active metabolites, in proportion to their receptor binding affinities.