The Effect of Different Digoxin Doses on Subjective Symptoms and Physical Working Capacity in Patients With Atrial Fibrillation

In a dose‐response study 14 patients with atrial fibrillation have been treated with increasing digoxin doses, 0.125, 0.25, 0.375, 0.50, 0.75 and 1.00 mg daily, until toxic symptoms or signs appeared. Dosage was changed every 14th day. The size of the doses was unknown to the patients. In this paper the effect on subjective well‐being and physical working capacity is presented. The mean “optimal” dose was 0.44 mg/day varying from 0.25 to 0.75 mg/day. An improvement was, however, achieved also at lower digoxin doses. The increase in physical working capacity, measured on a bicycle ergometer, was less impressive than the improvement in subjective well‐being and in physical capacity observed by the patients in their daily activities. Mean toxic dose was 0.65 mg/day. The toxic symptoms and some reasons for the great individual differences found in digoxin tolerance are discussed.