Effect of cimetidine on oral digoxin absorption.

Cimetidine is a commonly prescribed histamine 2-receptor antagonist used in the treatment of gastric acid-related disorders. Cimetidine can interact with a number of drugs, including theophylline, benzodiazepine sedative hypnotics, warfarin, and antiarrhythmics. Problems may occur in patients receiving drugs with a narrow therapeutic index when combined with cimetidine. Contrasting reports have been published on the potential interaction between digoxin and cimetidine. This study focuses on cimetidine's effect on the pharmacokinetic disposition of chronic digoxin usage. Six hospitalized patients with stable congestive heart failure received their usual maintenance dose of digoxin 0.125-0.25 mg/d po. After confirming steady-state digoxin concentrations, cimetidine 300 mg po q6h was administered. Two patients were dropped from the study. Analysis of digoxin serum concentrations, area under the curve, and the rate of elimination suggested no significant differences in digoxin parameters when combined with cimetidine.