Intravenous digoxin as a bioavailability standard: Slow infusion and rapid injection

Eight healthy male subjects received intravenous digoxin (0.75 mg) by rapid infection and by 1 hour infusion in a single‐dose crossover study. Multiple serum concentrations and 6 day urinary excretion of digoxin were determined by radioimmunoassay. Mean 6 day cumulative urinary excretion of digoxin after infusion (0.57 mg) was significantly greater than after rapid injection (0.52 mg). Between‐subject variability in urinary excretion after infusion was significantly less than that after rapid injection. Thus, administration of digoxin by slow infusion is preferable as an intravenous standard in bioavailability testing.