Monitoring of serum bioactivity levels of perazine and its metabolites by radioreceptor assay.

The bioactivity of perazine and its metabolites in human serum was analysed by radioreceptor assay. The IC50 value (the concentration eliciting a 50% blockade of 3H-spiroperidol binding to the dopamine receptor in a membrane suspension of porcine striatum) was for perazine 175 nmol/l, and for its metabolites perazine sulfoxide 1050 nmol/l, desmethylperazine 330 nmol/l, N-(3-phenothiazin-10-yl-propyl)-ethylenediamine 2800 nmol/l, and N-(3-phenothiazin-10-yl-propyl)-N'-methylethylenediamin 2850 nmol/l. Thus, perazine metabolites possess low affinity to the dopamine receptor. In a pilot study we measured the bioactivity of perazine and its metabolites in sera of perazine-treated psychiatric patients by radioreceptor assay and compared the results to levels obtained by high-performance thin-layer chromatography; the correlation coefficient r was 0.85 and the slope 0.95 (n = 11). Thus serum perazine can be adequately monitored by radioreceptor assay, as evidenced by the results from high-performance thin-layer chromatography.