Post-mortem distribution and tissue concentrations of digoxin in infants and adults

By means of 86Rb uptake inhibition assay, the distribution and tissue concentrations of digoxin in various tissues during maintenance therapy were studied post mortem in 12 infants (aged 5 days to 8 months) and 17 adults (aged 49-91 years). The mean maintenance dose for infants was 0.014 mg/kg bw/24 h and for adults, 0.005 mg/kg bw/24 h. The same relative distribution of the glycoside found in infants and in adults was: choroid plexus greater than ventricular myocardium greater than kidney greater than liver greater than skeletal muscle. Between infants and adults, the mean digoxin concentrations in choroid plexus, kidney, liver, and skeletal muscle did not differ significantly; however, significant differences were found in the glycoside concentrations in ventricular and in atrial myocardium. Both infants and adults showed a difference in the content of the glycoside within the heart, the concentration in ventricular muscle being significantly higher than in atrial. There seemed to be no direct relation between the tissue concentrations of the glycoside (myocardium, skeletal muscle) and the daily maintenance dose/mg/kg bw/24 h). The results suggest that the myocardial binding of digoxin is higher in infants than in adults.