The acute changes seen in cardiac glycoside receptor sites, 86rubidium uptake and intracellular sodium concentrations in the erythrocytes of patients during the early phases of digoxin therapy are not found during chronic therapy: pharmacological and therapeutic implications for chronic digoxin therapy.

1 Measurements of the binding of 12-alpha-[3H]-digoxin to the membranes of intact erythrocytes, erythrocyte 86rubidium uptake and intraerythrocytic sodium concentrations have been made in the red cells of various groups of patients--those who have not received digoxin, those during the early phases of treatment, those during chronic (greater than 2 months) treatment, and those toxic. 2 The values of those measurements in the patients in the early phases of therapy and in the toxic patients differed significantly from those of the untreated patients. 3 However, the values in the chronically treated patients were not different from those of the untreated patients. 4 The results suggest that the biochemical pharmacological effects of digoxin which occur during the early phases of therapy do not persist in the long-term. 5 The possible clinical significance of these observations is discussed.