[Clinical studies of the antiarrhythmic efficacy of disopyramide phosphate (Norpace) (author's transl)]

Abstract

The antiarrhythmic action of Norpace was investigated in three clinical studies. 1. A single blind placebo controlled study in 10 centers confirmed the antiarrhythmic action of Norpace in 120 patients with ventricular or supraventricular cardiac arrhythmias. It was shown by means of continuous ECG recordings that Norpace produced a statistically significant reduction in the frequency of both ventricular and supraventricular extrasystoles. Paroxysmal ventricular tachycardia was prevented in 70% of the patients. 2. In a double blind comparative study of Norpace and quinidine sulphate a similar antiarrhythmic action against ventricular and supraventricular extrasystoles was shown in both patient groups. In contrast, the tolerance of Norpace was markedly superior to quinidne sulphate. 3. An acute study of the action of Norpace was also conducted. Therapeutic plasma levels were attained within 2 1/2 hours following an initial single dose and within 60 to 120 minutes when this dose was doubled. Orally administered disopyramide phosphate has therefore proved effective in both the short and longer term treatment of various types of supraventricular and ventricular arrhythmias. Its antiarrhythmic properties are very similar to those of quinidine sulphate. The dosage of disopyramide phosphate should be sufficiently high and must be individualized. The dosage generally lies between 400 and 800 mg daily and should be given in 4 divided doses at intervals of 6 hours. To achieve rapid therapeutic effects an initial dose of 2 x 150 mg is recommended. This method of administration will produce effective therapeutic plasma levels within 1 to 2 hours. Due to possible negative inotropic effects it is necessary to digitalize patients with congestive heart failure and caution should be exercised in poorly compensated patients. Observed side effects were mainly of the anticholinergic type.