Quantitation of digoxigenin in serum following oral administration of digoxin in humans.

Separation of the acid breakdown products from digoxin in serum was accomplished by high performance liquid chromatography (HPLC). The major, less cardioactive, product digoxigenin was quantitated by several different commercial antisera from digoxin radioimmunoassay (RIA) kits. When two normal subjects were given digoxigenin (0.5 mg) orally appreciable concentrations were detected by digoxin RIA kit. Administration of a digoxin (0.5 mg) solution to the same overnight-fasted recumbent volunteers resulted in digoxigenin detection (HPLC-RIA) in serum only in one subject.