Phenothiazine-induced ECG abnormalities: effect of a glucose load.

A total of 54 schizophrenic patients, 27 male and 27 female, satisfying study criteria, were randomly assigned to one of three treatments: placebo; perphenazine, 20 mg/day; or the combination of amitriptyline, 125 mg/day, with perphenazine, 20 mg/day. Medication was administered under double-blind conditions for 12 weeks, after which ECGs were taken following an overnight fast and again following a 600-calorie meal. Among patients receiving perphenazine or amitriptyline-perphenazine, there was a statistically significant increase in repolarization abnormally after eating, whereas placebo-treated patients incurred no such increases. This supports the hypothesis that phenothiazine-induced ECG changes may be caused or facilitated by the glucose load. The incidence of increase in repolarization abnormality after the meal was higher among female patients than among male patients. The findings are of practical significance for readings of abnormality in the ECG of phenothiazine-treated patients.