Monitoring of Therapeutic Concentrations of Psychotropic Drugs in Plasma by Radioimmunoassays

Abstract

Sensitive and rapid radioimmunoassay (RIA) procedures for the determination of plasma concentrations of psychotropic drugs—chlorpromazine, Imipramlne, desipramlne, amitriptyline, and nortriptyline—are described. These procedures employing 20 to 200µl of plasma can determine subnanogram concentrations of these drugs and are shown to be suitable for therapeutic monitoring of these drugs in patients. For the antidepressant drugs, the RIA procedures were found to compare favorably with gas chromatographic procedures employing alkali flame ionization detectors. The RIA procedure for chlorpromazine measures chlorpromazine as well as its active metabolite, 7-hydroxychlorpromazine. Cross-reactivity profiles for the antiserum of each drug were obtained, and in each case the antiserum of the drug distinguished the drug from its inactive metabolites and most of the other psychotropic drugs tested.