Variation in Biologic Availability of Digoxin from Four Preparations

Abstract

The unexplained association of unusually large maintenance doses of digoxin and low serum digoxin concentrations in several patients prompted a study of the biologic availability of various digoxin products recently available for use on the wards of a New York City municipal hospital. In crossover studies in which 0.5 mg of digoxin was administered orally to normal volunteers, marked differences in serum digoxin levels achieved over a five-hour period were demonstrated. With one product peak serum levels were seven times those obtained with another. Significant variation between different lots prepared by a single manufacturer was also observed. Evidence of biologic as well as chemical equivalency of digoxin products for use in man should be required.