Serum concentration and serum half-life of digoxin in premature and mature newborns.

Serum concentrations and half-life times of digoxin were determined in ten mature and nine premature newborns. Median serum digoxin concentration was 2.3 ng/ml (1.2 to 3.5 ng/ml) in mature newborns and 2.4 ng/ml (1.5 to 4.5 ng/ml) in premature newborns. Median serum digoxin half-life was 35 hours (17 to 52 hours) in mature newborns and 57 hours (38 to 88 hours) in premature newborns. The difference in serum digoxin half-life between the two groups is statistically significant. The relatively long serum digoxin half-life in premature newborns is probably due to immature renal function in this group. The data emphasize the need for cautious digoxin administration, especially in premature infants.