Radioimmunoassay of dibenzazepines and dibenzcycloheptanodienes in body fluids and tissues.

In an attempt to establish a radioimmunoassay (RIA), imipramine and amitriptyline immunogens were prepared; desmethyl derivatives were converted into hemisuccinates, conjugated with bovine serum albumin and used for rabbit immunization. [3H]Amitriptyline (4.3 TBq/mmol) and [3H]imipramine (2.9 TBq/mmol) were prepared by catalytic dehalogenation or reductive alkylation. Dibenzazepines and dibenzcycloheptanodienes were determined in biological fluids by a direct method without deproteinization (lower detection limit of 0.5 microgram.l-1); using high-yield methods they were extracted from cell membranes. Assay of tricyclic antidepressants in humans showed that these substances disappear from plasma much earlier than from cell membranes. Dissociation of the antidepressants bound to cell membranes is slow and their plasma concentrations are not influenced by standing for 2 h at 4 degrees C. During preparing the membranes for binding studies these substances are not removed, and they may affect the results of the binding studies.