The use of practolol in supraventricular arrhythmias associated with acute illnesses

Supraventricular arrhythmias complicating acute illnesses were treated with intravenously administered practolol, a cardioselective beta adrenergic blocking agent. Slowing of atrioventricular conduction resulted in rapid control of ventricular rate in 23 of 33 episodes (70 percent) in 31 patients. Profound hypotension developed in two patients, presumably as a result of interference with adrenergic circulatory support. Serum levels from 19 patients showed no correlation with response to therapy and were much lower than levels previously reported necessary for slowing of tachycardias induced by isoproterenol and exercise. Response to practolol was maximum within 15 minutes and was not improved by additional dosage sufficient to raise serum levels. Practolol was a rapidly effective and safe antiarrhythmic agent in situations in which propranolol would be contraindicated and the risk of digitalis toxicity increased; it should be considered a primary drug for initiation of therapy for supraventricular tachyarrhythmias.