Long-term administration of probucol and QTc interval prolongation.

Electrocardiographic QTc intervals were measured in twenty-one hypercholesterolemic patients before and after long-term probucol (500-1,000 mg/day for 30 months) treatment. Probucol reduced serum total cholesterol (TC), triglyceride (TG), and high density lipoprotein-cholesterol (HDL-C). Mean QTc interval prolongation after probucol was 17 msec. A positive correlation was found between the change in QTc interval after probucol (delta QTc) and the total amount of probucol administered. delta QTc was negatively correlated to the pre-treatment QTc interval. No correlation was observed between serum probucol concentrations and delta QTc. Neither clinical evidence of cardiotoxicity nor critical arrhythmias were noted during the treatment period.