| Abstract: | The relationship between different maintenance doses and the steady-state digoxin blood concentration was studied in 160 patients with heart failure. All patients received digoxin tablets of the same brand (Digacin). The bioavailability of this brand is 82% compared with an i.v. standard. During the treatment with daily doses of 0.2 mg and 0.3 mg average serum digoxin levels of 1.09 +/- 0.45 ng/ml and 1.33 +/- 0.53 ng/ml were measured in patients with normal renal function. The daily dose of 0.4 mg digoxin was in correlation to an average serum level of 1.75 +/- 0.81 ng/ml. 81% and 86% of all patients with normal renal function taking 0.2 or 0.3 mg digoxin every day were found to have levels in the range of 0.7 to 2.0 ng/ml. The influence of sex, age, height, body weight, maintenance dose, serum creatinine and serum potassium on the variance of the digoxin plasma levels was computed by multiple linear regression. The multiple correlation coefficient was r = 0.666, the coefficient of determination (100 r2) being 44.4%. Therefore 44.4% of the total variance could be explained by these variables. Individual variables accounted for the following percentages of the total variance: serum creatinine 29.1%; maintenance dose 14.5%; age 4.3%; and reciprocal of body weight 3.9%. |
