Absorption of digoxin in infants.

The bioavailability of digoxin in solution was studied in 4 newbron infants with heart failure. Serum digoxin concentrations were determined by radioimmunoassay using 125I. Bioavailability was estimated by camparison of the areas under the 8-h serum concentration curves (8-h AUC) after intravenous and oral administration of the glycoside. After oral administration of digoxin (1/4 of the digitalizing dose, 0.05 mg/kg bw), peak serum values of 2.3-4.4 ng/ml were reached within 30-90 min. After intravenous administration of the same amount of the glycoside, there was a rapid decrease in serum concentration during the first 2 h, and after about 4 h the serum concentration curves paralled those obtained after oral dosing. Based on within subject comparison of intravenous and oral 8-h AUC'S, the mean bioavailability of digoxin was estimated to be 72 per cent (range 52-79 per cent). It was concluded that digoxin in solution, given to infants with mild to moderate heart failure, is well absorbed and biologically available to the same extent as in adults.