Serum digoxin levels in neonates, infants and children with heart disease

Abstract

Serum digoxin levels were measured in 53 neonates and infants receiving 18-22 microgram/kg/day (high dose) oral maintenance digoxin, and 44 neonates, infants and children receiving less than 18 microgram/kg/day (low dose) oral maintenance digoxin. In both groups, patients under four months of age had significantly higher serum digoxin levels than older patients, in the high dose group 2.6 ng/ml compared with 1.4 ng/ml and in the low dose group 2.2 ng/ml compared with 1.0 ng/ml. Correlation between digoxin dosage and serum level was weak and unaffected by blood urea level. Only two patients in the entire series showed toxic manifestations. Sixteen patients had serum digoxin levels measured before and after corrective cardiac surgery while receiving comparable dosages of digoxin. Despite lower serum digoxin levels postoperatively pulse rates fell significantly, illustrating the influence of changing haemodynamic status on the inter-relationships of digoxin dosage, serum levels and clinical response. Recommended dosage regimens are outlined.