The evaluation of a radioimmunoassay for phenothiazines and thioxanthenes using an iodinated tracer.

Antisera have been raised in rabbits to the immogen 2-trifluoromethylphenothiazine-10-beta-propionate bovine serum albumin. An [125I]-labelled tyrosine methyl ester derivative of the immunogen precursor has been synthesised and used with the antisera to develop a simple, precise and sensitive radioimmunoassay for phenothiazines and thioxanthenes bearing 2-trifluoromethyl substituents. The assay can detect 0.4 ng/ml of fluphenazine, trifluorperazine or (Z)-flupenthixol in 100 microliter of human serum without interference from their sulphoxide or 7-hydroxylated metabolites. An acceptable correlation between this assay and an established fluphenazine radioimmunoassay using commercial [3H]fluphenazine has been obtained for plasma samples.