Edrophonium has been reported to be valuable in the differentiation of supraventricular tachycardia. To evaluate the clinical usefulness of edrophonium, 10 mg. of it was given intravenously to 103 patients with various arrhythmias. The electrocardiogram was then monitored for 30 minutes after administration of the drug. Edrophonium had no effect in 13 patients with atrial tachycardia, 3 developed atrial tachycardia with block, 3 showed a decrease in rate, and 1 developed atrial fibrillation. Twenty-six of the twenty-seven patients with atrial fibrillation showed a decrease in the ventricular response. Eight patients with atrial flutter had no response, 1 showed transient asystole, and 4 increased the block. Of the 21 cases of sinus tachycardia, 18 showed, 2 showed no response, and in 1 the rate increased.

The maximum effect was seen within 2 to 3 minutes. By 15 to 20 minutes the baseline electrocardiogram was again observed. Side effects included abdominal discomfort, nausea, blurring of vision, lacrimation, and leg cramps.