[Digoxin concentration in the blood during the treatment of cardiac insufficiency]

Blood concentrations of Digoxin were determined by radioimmuno-assay in 80 patients with different stages of circulatory insufficiency receiving maintenance therapy with Digoxin, 0.25-0.75 mg/day. The range of Digoxin concentration fluctuations is very wide--from 0.25 to 2.4 ng/ml. Some elevation of Digoxin concentration in blood was observed when the dose of the drug was increased, both in different groups of patients, and in the same patients when the maintenance dose was altered. Studies conducted during digitalis intoxication in 4 patients demonstrated different levels of Digoxin concentration in blood--from 0.8 to 2.6 ng/ml. The obtained results permitted to conclude that the concentration of Digoxin in blood has no significance in choosing the optimum therapeutic dose, unless the clinical data are taken into account.