Ventricular arrhythmia associated with the administration of thioridazine hydrochloride is thought to be the cause of death of a 19-year-old boy. There were changes in the repolarization portion of the electrocardiogram. High doses of thioridazine had been given in cases with fatal or nearly fatal outcomes, and there is a strong suggestion that when high doses of phenothiazines are required, thioridazine should be considered contraindicated.
Giles TD, Modlin RK. Death Associated With Ventricular Arrhythmia and Thioridazine Hydrochloride. JAMA. 1968;205(2):108-110. doi:10.1001/jama.1968.03140280062021