Paradoxical ventricular tachycardia and fibrillation after intravenous bretylium therapy. Report of two cases.

Two patients were treated with bretylium tosylate for malignant ventricular arrhythmias after inadequate response to conventional agents. In the first patient, two episodes of ventricular tachycardia requiring cardioversion occurred in close temporal sequence with administering bretylium. With drug rechallenge two days later, ventricular tachycardia recurred within minutes. In the second case, five cardiac arrests due to ventricular tachycardia and fibrillation occurred during several hours after beginning a trial of bretylium maintenance therapy for complex ventricular ectopy. Although transient increases in ectopy after bretylium therapy have been described, presumably due to catecholamine release, the occurrence of life-threatening ventricular arrhythmia leading to cardiac arrest has not previously been emphasized. There is potential for this side effect, and additional caution in the use of this drug should be followed.