The gastrointestinal uptake of methyldigoxin-12α-³H in man

Summary

Methyldigoxin-12α-³H and the nonabsorbable marker polyethylene glycol (PEG) were administered orally to five healthy subjects. Comparison of the radioactivity per mg PEG in gastrointestinal aspirates and the test solution (A/T ratio) showed that approximately two thirds of the label had been absorbed during its passage through the duodenum and the upper jejunum. The urinary recovery of label was 68–85 per cent. There was evidence of biliary excretion of label, not exceeding 15 per cent during the first day. The total absorption of radioactivity amounted to 75–90 per cent. The uptake of label did not reflect the absorption of³H-methyldigoxin. Part of the³H-methyldigoxin was hydrolysed in the stomach, a reaction which resulted in the formation of labelled compounds tentatively identified as digoxigenin and its derivatives with one to three digitoxose moieties. — The major part of the urinary and biliary label appeared to be attached to methyldigoxin (26–60 per cent) and digoxin (31–59 per cent). The degree of demethylation was approximately the same after oral administration as after intravenous injection of³H-methyldigoxin in one subject.