TORSADES-DE-POINTES VENTRICULAR-TACHYCARDIA ASSOCIATED WITH OVERDOSE OF ASTEMIZOLE

An overdose of astemizole predisposes the myocardium to ventricular dy srhythmias, including torsades de pointes. Herein we describe a case o f astemizole-induced torsades de pointes ventricular tachycardia and a lso review previous case reports in the literature. All the patients w ere young, and dysrhythmias developed only in those with corrected QT intervals greater than 500 ms. Although several mechanisms have been p ostulated, no clear explanation has been provided for why astemizole p romotes myocardial dysrhythmias. Treatment of astemizole-induced torsa des de pointes includes discontinuing use of astemizole, intravenous a dministration of magnesium sulfate and isoproterenol, temporary cardia c pacing, and, when necessary, direct current cardioversion. A cardiac cause of syncope or convulsions must not be overlooked, especially in patients taking H-1 antagonists because they often have these symptom s before hospitalization or detection of torsades de pointes (or both) .