Comparison of the serum protein binding of digoxin in premature and mature newborns, infants and adults.

Infants require higher therapeutic doses (per unit body weight and surface area) and also tolerate higher doses of digoxin than adults. In contrast premature and even mature newborns are more susceptible to digoxin intoxications. Serum protein binding contributes to the apparent volume of distribution. Since the volume of distribution for digoxin shows an age-dependency, the present study was designed to determine the plasma protein binding of digoxin in premature and mature newborns as well as in infants and adults. Using the equilibrium dialysis method the fraction of digoxin bound to serum protein averages 30% in all groups studied. Thus protein binding could not account for the differences in dosage and susceptibility of digoxin in newborns and infants as compared to adults.