The pharmacokinetics of digoxin and metildigoxin were investigated in geriatric patients on maintenance treatment. Minimum serum glycoside concentrations were determined on 3 consecutive days, and the elimination rate over a withdrawal period of 4 to 6 days was studied.In patients with serum creatinine levels of ≤ 1.3mg/dl, the oral standard dose (D1) of digoxin necessary for a minimum serum concentration of 1.0ng/ml was 1.4 times higher than that of metildigoxin. There was no significant difference in the elimination rate of both glycosides.The pharmacokinetics of metildigoxin were further investigated in patients with elevated serum creatinine levels. The standard dose was best correlated with the creatinine clearance, calculated from the serum creatinine, age, weight and sex of the patients. The apparent volume of distribution of metildigoxin decreased with the drug's total body clearance.