EFFECT OF PHENOTHIAZINES ON ELECTROCARDIOGRAM

  • 1 January 1964
    • journal article
    • research article
    • Vol. 91  (10) , 537-+
Abstract
Thioridazine, chlorpromazine and trifluoperazine were administered to 6 psychiatric patients. Each was used in 4 dosage levels (thioridazine and chlorpromazine: 200, 400, 800 and 1200 mg daily; trifluoperazine: 8, 16, 32, 64 mg daily); and each increase in dosage was effected after 4 days of drug administration. Before the trial, twice during each drug period and before commencement of the next dose regimen, an electrocardiogram (ecg) was recorded. The findings indicated that thioridazine modifies the terminal portion (S-T segment, T and U waves) of the human ecg. A similar change occurred in three of 6 subjects while taking chlorpromazine and in one of 6 while taking trifluoperazine. Thioridazine induced changes in all 6 subjects studied, viz., blunting and notching of T waves with or without prolongation of QT interval. In some the notching produced a double-hump appearance in which a T wave of reduced voltage formed the proximal hump and a positive U wave of increased voltage formed the distal hump. Thioridazine-induced alterations in the ecg were described as resembling those caused by quinidine; they also resemble changes associated with hypo-kalemia.