Probucol-induced QT prolongation and torsades de pointes.

Probucol administration of 4 weeks produced torsades de pointes associated with exacerbated QT interval prolongation in a 36-year-old woman with Romano-Ward syndrome. With discontinuance of probucol, the QT interval corrected for rate shortened from 620 msec to 500 msec and ventricular ectopic beats disappeared completely. Although probucol is known to prolong the QT interval, associated ventricular tachyarrhythmia has not been reported in humans as yet. This case suggests that one should be very careful in the administration of probucol to patients with long baseline QT intervals.