Torsade de pointes associated with Astemizole overdose treated with magnesium sulfate.

Astemizole (Hismanal-Janssen, New Brunswick, NJ) is a nonsedating antihistamine that has the advantage of a once-daily dosage schedule. This article reports the case of a 14-year-old female who intentionally ingested 270 mg of Astemizole and developed torsade de pointes, a form of polymorphic ventricular tachycardia that is associated with prolongation of the QTc interval. She was successfully treated with magnesium sulfate infusion and had an uneventful recovery over a period of 36 hours. This case illustrates that Astemizole overdose is not benign and should be considered in the differential diagnosis of ventricular tachyarrhythmias. Use of high-dose Astemizole may not be advisable for patients who are at risk for prolongation of the QTc interval.