Plasma concentrations of thioridazine metabolites and ECG abnormalities.

Five acute schizophrenic patients were given a standard thioridazine dose (4 mg/kg/day po). Their plasma concentrations of thioridazine and its metabolites were determined by GLC, and their ECG's were recorded routinely. In four of the five patients, abnormal ECG's (malformation of the T-wave or lengthening of the repolarization time) were found whenever plasma concentrations of the thioridazine ring sulfoxide were elevated. No relationship could be detected between the appearance of ECG abnormalities and the concentrations of thioridazine and its other metabolites.