Prolonged recurrence of pentamidine-induced torsades de pointes

OBJECTIVE: To report a case of recurrent pentamidine-induced torsades de pointes (TdP) and to review previously reported cases in the literature. DATA SOURCES: Medical records of the subject patient, case reports, and relevant studies identified by MEDLINE. DATA EXTRACTION: Data were abstracted from pertinent published sources by one author and reviewed by the remaining authors. DATA SYNTHESIS: A 43-year-old woman with AIDS experienced pentamidine-induced TdP. TdP and other cardiac arrhythmias recurred repeatedly for 13 days after pentamidine therapy was discontinued and in the presence of normal magnesium and potassium serum concentrations. Infusions of magnesium, lidocaine, and isoproterenol were used to treat the arrhythmias. The exact mechanism of pentamidine-induced TdP has not been clearly established. It is postulated, however, that the similarity of pentamidine's structure to procainamide may contribute to its proarrhythmic effects. The tissue-binding capacity of pentamidine may result in a prolongation of its effects. No distinctive characteristic appears to predispose people to the development of cardiac arrhythmias. Laboratory values that should be monitored include serum magnesium, potassium, and creatinine. The corrected QT interval also should be monitored. CONCLUSIONS: Recurrent arrhythmias may be seen for many days after intravenous administration of pentamidine has been discontinued. Clinicians should consider this phenomenon as they decide how to monitor patients who have received this drug.

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