The evaluation of potential in vitro interaction between dietary fiber components and digoxin

The elderly population comprise the largest group of persons using the cardiac glycoside digoxin, which is prescribed for the treatment of congestive heart failure. The elderly also are encouraged to increase their dietary fiber intake to regulate intestinal elimination and to prevent such ailments as constipation and diverticular disease. An interference with absorption of digoxin has been demonstrated with the concurrent use of antacids, cholestyramine and bran cereal. The purpose of this study was to examine the possibility of in vitro digoxin binding to various dietary fiber components. Crystalline digoxin powder was exposed to bran, pectin, lambda carrageenan, sodium pectinate, sodium carboxymethylcellulose and xylan in separate experiments by column chromatography. The fractions were collected and analyzed using an isocratic, reversed-phase HPLC system. The mean recovery of digoxin after exposure to the different fiber components ranged from 79 percent (xylan) to 100 percent (lambda carrageenan). Data analysis indicated no significant differences (p>0.05) between the means of the fiber groups. These results suggest an interaction (binding) does not occur in vitro between digoxin and the fibers investigated.