Potential use of a radioreceptor assay for the determination of benzodiazepine compounds in serum.

The clinical monitoring and intensive care of patients who have taken an overdose of a benzodiazepine require rapid and quantitative methods to assess benzodiazepine concentrations in biological fluids. A radioreceptor assay (RRA) permits the simultaneous measurement of the benzodiazepine molecules that bind to the receptor, providing a total estimate of all pharmacologically active forms of the drug(s) (parent drug and active metabolites). This study describes the development of an RRA for the determination of benzodiazepine compounds in serum using a lyophilized bovine brain cerebral cortex receptor preparation. The standard curves and the sensitivity of this RRA are determined for 20 different benzodiazepines and the specific antagonist flumazenil. The sensitivity ranges from 5 ng/mL for clonazepam to 3500 ng/mL for chlordiazepoxide. The IC50 values are significantly correlated (r = 0.81) with the lowest recommended therapeutic concentrations. The advantages and disadvantages of this RRA are discussed and compared with those of other chromatographic and immunological methods.