DIGOXIN IN THE ELDERLY AND IN RENAL-FAILURE - CONTRIBUTION OF ERYTHROCYTE RB-86 UPTAKE TESTS

Abstract

Na+, K+-ATPase activity was assessed indirectly in 3 groups of subjects of differing age and in a group of patients with renal failure, by measuring the 86Rb uptake in the patients'' own erythrocytes. The inhibiting action of digoxin on this activity was measured in vitro. Erythrocyte 86Rb uptake was found to be lower in the elderly as was the calculated volume of distribution of digoxin. Sensitivity to the inhibiting action of digoxin increased with age. In the renal failure group 86Rb uptake was diminished and the sensitivity to digoxin was variable. Na+, K+-ATPase activity could be 1 determinant of the volume of distribution of digoxin. Quantitative and qualitative changes of this enzyme could explain features of the pharmacokinetics of digoxin in renal failure and in old age.