Bioavailability of digoxin from tablets. IV. Urinary excretion of digoxin during multiple dose treatment
Nyberg, L.; Andersson, K.E.; Fagerström, P.O.
Acta Pharmaceutica Suecica 14(2): 119-136
1977
ISSN/ISBN: 0001-6675 PMID: 906830 Document Number: 119284
Three commercial digoxin tablets, covering a wide range of dissolution rates, were studied in healthy volunteers during continuous treatment. An i.v. dose was administered for reference. At each tablet treatment, urinary digoxin was measured during 3 discrete dosage intervals. After i.v. administration, 7 days sampling of urine was performed and the infinite excretion calculated by extrapolation. Particular attention was paid to the handling of the samples to avoid losses of drug by adsorption. The digoxin content was determined by radioimmunoassay. On the average, 75.7% of the bioavailable drug was calculated to leave the body via the renal route. The mean half-life was 44.4 h. Mean bioavailabilities from the preparations ranged from 66.6-39.5%. The influence of dissolution rate on the absorption was pronounced only at slow dissolution. Subjects absorbing less than average digoxin seemed to be particularly sensitive to differences in the dissolution rate.