Extrarenal clearance, distribution volume, and elimination rate of digoxin and metildigoxin in anuric patients

The pharmacokinetics of 3H-labeled digoxin and metildigoxin were compared in six anuric patients. The following means +/- s.e.m. were obtained: extrarenal clearance of digoxin, 43.3 +/- 5.4 ml/min, of metildigoxin, 30.3 +/- 2.9 ml/min; distribution volume of digoxin, 315 +/- 29 1, of metildigoxin, 258 +/- 22 1; rate constant for elimination of digoxin, 0.0086 +/- 0.0013 h-1, of metildogixon, 0.0071 +/- 0.0007 h-1. The elimination rates correspond to half-lives of 80 h for digoxin and of 97 h for metildigoxin. From our investigations and published data a weighed mean of 47 ml/min was calculated for the extrarenal clearance of metildigoxin. This is not significantly different from the mean extrarenal clearance of 40 ml/min reported for digoxin. A total body clearance of 40 ml/min and a daily intravenous dose of 0.1 mg correspond to an average steady-state glycoside concentration of 1.74 ng/ml.