On the fate of orally administered3H-Lanatoside C in man

Summary An aqueous solution of³H-Lanatoside C and polyethylene glycol (PEG, a nonabsorbable marker) were administered orally to five subjects. The ratio between the radioactivity per mg PEG of gastrointestinal aspirates and the test solution showed that 10–30 per cent of the label was absorbed in the duodenum and upper jejunum. The urinary recovery of 38 to 57 per cent of the radioactivity indicated additional uptake of label in more distal parts of the intestines. The biliary excretion of label during the first day was estimated to be about 10 per cent. The total gastrointestinal absorption of radioactivity was calculated to be 40–65 per cent. — Due to acid hydrolysis in the stomach, a minor amount of³H-Lanatoside C was transformed, mainly to compounds tentatively identified as³H-digoxigenin and³H-digoxigenin-monodigitoxoside. — The major labelled compounds in the urine and the bile after oral administration appeared to be³H-digoxin and³H-desgluco-Lanatoside C. In one subject, who received³H-Lanatoside C intravenously, most of the label was excreted unchanged.On incubation with fresh faeces,³H-Lanatoside C was rapidly converted to compounds tentatively identified as³H-desgluco-Lanatoside C and³H-digoxin