Tritiated digoxin. XIV. Enterohepatic circulation, absorption, and excretion studies in human volunteers.

SUMMARY Metabolic turnover studies performed on six patients with surgically induced biliary fistula given tritiated digoxin reveal virtually all stool excretion of digoxin to be derived from bile. This establishes the relative lack of recycling of digoxin as an important factor in digoxin metabolism. This is probably related to its polar chemical structure and is a determinant of its clinical duration of action in human subjects. The amount of digoxin in the enterohepatic circulation (recycling) was calculated to be 6.5% of the administered dose and absolute absorption to be 85% in human subjects. Additional Indexing Words: Biliary fistula Digoxin, metabolism of T HE availability of 3H digoxin for experimental clinical use has made possible a number of meaningful studies during the last decade.1-17 These studies have outlined the serum tumover rates, serum half-time (the time required for one half of the radioactivity identified with the drug to disappear from the serum) and serum digoxin levels. The urinary and fecal excretion of digoxin was characterized , and the larger portion of the drug was found to be excreted unchanged in the urine.