The effect of digoxin on the serum potassium concentration

In recent studies on the influence of muscular and symphatoadrenergic activity on digoxin pharmacokinetics, the serum potassium concentration was found to increase during 2 h of supine rest in digitalized healthy subjects and out-patients. The present study was made in order to find out whether this change in serum potassium concentration is dependent on inhibition of the Na-K-ATPase activity by digitalis treatment. Ten healthy subjects were investigated on two separate occasions: before and after digitalization with digoxin 0.37-0.50 mg daily for 10 days. Serum potassium and digoxin concentrations were analysed before and after 2 h of rest in the sitting position. Without digoxin treatment, no change in serum potassium concentration was seen. During digoxin treatment, the serum potassium concentration increased by 0.19 +/- 0.23 mmol(l)-1 (p < 0.05) during the period of rest. Thus, a digitalis-induced depression of Na-K-ATPase activity seems to be a prerequisite for the described change in serum potassium concentration.