A study of the kinetics of chlorpromazine sulfoxide by a specific radioimmunoassay after a single oral dose of chlorpromazine in healthy volunteers.

Antibody specific for chlorpromazine sulfoxide (CPZSO) was produced in rabbits immunized with a hapten-bovine serum albumin conjugate, which was prepared by linking the 10-alkyl side chain of CPZSO to the protein molecule via a 2-carbon bridge. A simple radioimmunoassay was developed which can measure less then 20 pg of CPZSO in plasma. The assay has adequate specificity so that isolation of CPZSO is unnecessary. It was used together with a previously developed chlorpromazine (CPZ) radioimmunoassay to determine the concentrations of CPZ and CPZSO in plasma samples from five healthy volunteers after they had received a single 50-mg oral dose of CPZ. The plasma level data reported here support the previous findings that a significant portion of CPZ is metabolized to CPZSO during presystemic absorption. There are, however, differences to those previously reported in the plasma concentration ratios of CPZSO to CPZ. The possible reasons for these differences are discussed.