Disposition of tablet and capsule formulations of digoxin in the elderly.

ABSTRACT

STUDY OBJECTIVE: To compare digoxin tablets and liquid-filled capsules with respect to excretion of the drug and its metabolites in urine and feces at steady state. DESIGN: A randomized, crossover trial, each period lasting 3 weeks, with no washout period. SETTING: A university hospital. PATIENTS Six patients, five of whom were elderly, with histories of gastrointestinal disorders, such as hypochlorhydria, intestinal bacterial overgrowth, and inflammatory bowel disease. INTERVENTIONS: The patients received digoxin once/day in either tablet or capsule form 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 and capsules in recovery of digoxin or its metabolites in urine or feces (p = 0.05). One subject had a 4-fold increase in urinary drug excretion and 50% decrease in fecal excretion after taking the capsules compared with tablets. Intersubject variability in extent and type of metabolite excretion was greater than intrasubject variability. CONCLUSIONS: Fecal analyses may be an accurate way to classify patients as formers of digoxin reduction products.