Oral phentolamine for treatment of ventricular premature contractions.

Phentolamine was administered orally to 21 patients with persistent ventricular premature contractwons. In I5 patients the ventricular premature contractions were abolished, while in 5 a conspicuous decrease in their frequency was observed. The effective dose of phentolamine was either 50 or 75 mg. administered 4 times a day in all but 2 of the patients. The maximum antiarrhythmic effect was seen in 2 or 3 days in the majority ofpatients. Thefavourable antiarrhythmic effects persisted in all of the successfully treated patients when they were treated for an additional week. The drug produced transient gastrointestinal symptoms in 3 patients. Hypotension was not observed. These studies indicate that phentolamine warrants further study as an antiarrhythmic agent.