Steady state serum digoxin concentration in relation to digitalis toxicity in neonates and infants.

Steady state serum digoxin concentrations were determined in 34 neonates and infants receiving standard maintenance doses of the drug. Digitalis intoxication, diagnosed by ECG criteria, occurred in four of 13 patients with a serum concentration above 2 ng/ml and not in any of 21 subjects with a serum digoxin concentration below this level. This association was found to be significant. It seems that the concept of increased tolerance to digoxin hitherto ascribed to infants is not tenable and that the monitoring of serum digoxin concentration is essential to treatment in this age group.