Thioridazine 5-sulfoxide diastereoisomers in serum and urine from rats and man after chronic thioridazine administration.

Two diastereoisomeric pairs of thioridazine 5-sulfoxide (T5SO)(ring sulfoxide) were detected in serum and urine from rats and patients following chronic thioridazine administration. The isolation and identification of each pair of isomers was by thin layer chromatography, high pressure liquid chromatography, and mass spectrometry. Equal concentrations of T5SO pairs were present in serum and urine specimens from both rats and man. Therefore, the biotransformation and renal clearance of the isomers does not appear to be stereoselective in either species. An evaluation of chromatographic systems used in previous metabolic studies of thioridazine, and reasons for the lack of prior recognition of thioridazine 5-sulfoxide isomers is also presented.