– Kaolin-pectateand bran: The decrease in digoxin absorption can be abolished by giving digoxin 2 hours before administration of the antidiarrheal agent or may be minimized by administration of the capsule formulation of digoxin When digoxin was given at the beginning of a meal containing a high content of fiber, there was a 20% decrease in cumulative 6 day urinary digoxin excretion . The decreased bioavailability of digoxin as a result of the coadministration of an antidiarrheal suspension containing 18% kaolin and 0.4% pectin (Kaopectate) was first reported by Binnion after observing ineffective blood levels of digoxin in a patient who had taken the antidiarrheal at the same time as digoxin.Others were not able to document a decrease in digoxin absorption when digoxin was given 15 to 30 minutes before a meal containing high fiber content.

– Antimicrobial drugs. : In a recent study, a 5 day course of erythromycin or tetracycline was found to raise the serum digoxin concentrations by 43 to 116% in three volunteers who produced large amounts of digoxin reduction products (> 35 to 40% of total urinary digoxin and its metabolites). Administration of digoxin in capsule form decreases the percent of digoxin reduction products formed, presumably by more complete absorption of digoxin in the small intestine . The reduced metabolites virtually disappear from the stool and urine after therapy with certain antibiotics, and this can lead to an increase in bioavailability of digoxin . Certain antimicrobial drugs such as neomycin, sulfasalazineand paraaminosalicylic acid (PAS), often used for their effect on intestinal function and flora, appear to depress digoxin absorption. This interaction results in an 18 to 28% decrease in the bioavailability of digoxin and is not minimized by temporal separation of the time of administration of dig