Digoxin metabolism in the elderly.

Tritiated digoxin (0.5 mg) was given intravenously to five elderly men (mean age, 77 years) and nine young men (mean age, 27 years). The elderly were not in congestive heart failure. The serum creatinines of the old and young were not different. However, the creatinine clearance averaged 56 ml/min/ 1.73 m2 in the old and 122 ml/min/1.73 m2 in the young (P < 0.001). Digoxin clearance averaged 53 ml/min/ 1.73 m2 in the old and 83 ml/min/1.73 m2 in the young (P < 0.001). The blood concentrations of tritiated digoxin were significantly higher in the elderly throughout the study (P < 0.05). When blood digoxin concentrations were corrected for body surface area, there was no significant difference between the two groups during the first 24 hr, but thereafter the concentrations in the elderly were higher. The same dose of digoxin resulted in higher blood concentrations and longer blood half-life in the elderly. This is due to the smaller body size and a diminished urinary excretion of digoxin in the elderly.