Absorption of digoxin in severe right heart failure.

The absorption of digoxin has been investigated in 8 patients before and after successful treatment of severe right heart failure. 3H-digoxin 0.1 mg as a solution, and un-labelled digoxin 0.25 mg as a tablet, were given to fasted patients. Blood samples were taken at various time intervals up to 120 hours and urine was collected over the same period. The concentrations of labelled digoxin in plasma and urine were measured in a liquid scintillation counter, unlabelled digoxin was estimated by radioimmunoassay, and various pharmacokinetic parameters were calculated. There was no significant difference in the plasma concentration curves in severe right heart failure and after its successful treatment, nor did any of the calculated pharmacokinetic parameters change significantly. Therefore, inhibition of the absorption of digoxin appears unlikely. In an additional study to estimate absolute bioavailability two different groups of patients in severe right heart failure were given 3H-digoxin 0.1 mg or unlabelled digoxin 0.25 mg i.v. and the pharmacokinetic parameters were compared with those from the previous study. The bioavailability of the 3H-digoxin solution and of the digoxin tablet were in the same range as values previously published for healthy volunteers, and patients both with and without cardiac failure.