Decreased Bioavailability of Digoxin Due to Antacids and Kaolin-Pectin

Abstract

Employing a Latin-square design and single-dose studies of bioavailability in 10 normal human volunteers, we tested the hypothesis that antacids and kaolin-pectin might interfere with the bioavailability of orally administered digoxin. Cumulative six-day urinary digoxin excretion (expressed as the percentage of a 0.75-mg dose recovered) was: control, 40.1 ±3.0 (S.E.); aluminum hydroxide, 30.7±2.9; magnesium hydroxide, 27.1 ±2.4; magnesium trisilicate, 29.1 ±1.7; and kaolin-pectin 23.4±2.0. The differences in means were highly significant (F = 10.47, P<0.005). Further analysis (multiple comparison test) revealed that control differed significantly from each of the other treatments (α = 0.05), but there was no such difference between any of the other treatment groups. The decreased cumulative excretion produced by antacids and kaolin-pectin reflected a striking reduction in digoxin absorption associated with these compounds that was not related to alteration of gut transit time or to adsorption of digoxin to these gastrointestinal medications. (N Engl J Med 295:1034–1037, 1976)