DISPOSITION OF TABLET AND CAPSULE FORMULATIONS OF DIGOXIN IN THE ELDERLY

Study Objective. To compare digoxin tablets and liquid-filled capsules with respect to excretion of the drug and its metabolites in urine an d feces at steady state. Design. A randomized, crossover trial, each p eriod lasting 3 weeks, with no washout period. Setting. A university h ospital. Patients. Six patients, five of whom were elderly, with histo ries of gastrointestinal disorders, such as hypochlorhydria, intestina l bacterial overgrowth, and inflammatory bowel disease. Interventions. The patients received digoxin once/day in either tablet or capsule fo rm for 3 weeks, and then were switched to the other formulation. Total urinary and fecal excretion from the last 3 days of each regimen were analyzed for the drug and metabolites. Measurements and Main Results. No statistically significant differences were found between tablets a nd capsules in recovery of digoxin or its metabolites in urine or fece s (p=0.05). One subject had a 4-fold increase in urinary drug excretio n and 50% decrease in fecal excretion after taking the capsules compar ed with tablets. Intersubject variability in extent and type of metabo lite excretion was greater than intrasubject variability. Conclusions. Fecal analyses may be an accurate way to classify patients as formers of digoxin reduction products.