Serum Levels of Digoxin and Endogenous Factor in the Newborn
The aim of this study was to analyze the presence and possible interference of a digoxin-like, immunoreactive endogenous substance with measurement of digoxin levels in the newborn. We intended to assess the correlation between serum levels of digoxin therapy with acute (0.03 mg/kg) plus maintenance (0.01 mgr/kg/day) doses, therapy with maintenance doses only, and clinical and electrocardiographic (ECG) signs of digitalis toxicity. Serum levels of digoxin were analyzed with solid phase radioimmunoassay (RIA) (commercial kit of clinical assays) in 40 newborns with a gestational age from 28–42 weeks (mean, 38.5 weeks; SD, 3.8 weeks) and birth weight from 1,800–4,250 grams. Thirty-eight patients had a diagnosis of congenital heart disease and two had a cardiac rhythm disorder.