Bioavailability of different lots of digoxin tablets from the same manufacturer

The bioavailability of single doses from 4 randomly selected lots of digoxin from a single manufacturer that were recently marketed in the United States was compared. In a crossover study in 6 normal volunteers, serum digoxin concentrations for 0 to 6 hr and urinary glycoside excretion for 24 hr after 0.5-mg doses were measured by radioimmunoassay. The variation in bioavailability between the 4 lots was no greater than that seen when one of them was taken twice. Intersubject variation in areas under the serum concentration-time curves and in the 24-hr urinary digoxin measurements was more than twice that of intrasubject variation. The variability of the urinary digoxin determinations was somewhat less than that of the areas under the serum concentration-time curves.