Studies were performed in 20 patients with symptomatic
ventricular tachycardia (VT) to determine the efficacy of
bethanidine compared with
procainamide in preventing VT induced by programmed electrical stimulation. Before administering
bethanidine, 5 to 10 mg/kg, the patients received 15 mg of
protriptyline orally 24 and 2 hours before electrophysiologic studies to prevent the orthostatic hypotensive effects of
bethanidine. Sustained VT (VT not spontaneously stopping) was induced in 8 and nonsustained VT (10 beats or more, terminating spontaneously) was induced in 4 patients.
Bethanidine, 5 mg/kg, protected in 7 patients, and 10 mg/kg protected 1 additional patient.
Procainamide, 1,000 and 1,500 mg intravenously, protected 8 of 16 patients.
Bethanidine prevented VT induction in 50% of the patients not protected by
procainamide.
Bethanidine facilitated VT induction in 3 patients, while
procainamide facilitated VT induction in 1 patient. Four patients with symptomatic VT have received
bethanidine therapy for an average of 11 +/- 1.3 months, without clinical recurrence of their VT. Concomitant administration of
protriptyline attenuated the acute hemodynamic changes caused by
bethanidine and chronic combined
therapy of
protriptyline and
bethanidine abolished the severe orthostatic changes in blood pressure caused by
bethanidine. These studies show that
bethanidine is effective in preventing VT induction and, thus, its use may not be restricted only to cases of primary
ventricular fibrillation.