Serial serum digoxin concentrations were measured over a 10-day period in 15 low birth weight infants requiring digoxin therapy. The calculated total body digoxin clearance (TBDC) was found to be highly dependent on gestational age and body weight, with dose-normalized, steady-state digoxin concentrations inversely related to the same factors. Because of the decreased TBDC in low birth weight infants, our data support the recent recommendations in the literaure to reduce maintenance doses of digoxin in these infants. Our study has further demonstrated that the reduction should be proportional to both gestational age and body weight.

Digoxin pharmacokinetics were studied in 13 low-birth-weight infants requiring digoxin therapy. Their weights ranged from 820 to 2,710 g (x̄ = 1,440 g) and gestational ages ranged from 26 to 38 weeks (x̄ = 30.9 weeks). The distribution and elimination of digoxin can be described by an open two-compartment model. Poor correlation between volume of distribution Vdβ (5.7 ± 1.0 liters/kg) and gestational age (GA) or weight (Wt) was observed. Digoxin half-life (47 ± 21 h) was inversely related to GA and Wt (r = 0.69 and 0.66, respectively), but total body digoxin clearance (29.8 ± 14.7 ml/min/1.73 m^2) was found to be highly dependent on these two variables (r = 0.87 and 0.88, respectively). According to the results of this study and our previous investigation, digitalizing and maintenance dosages of digoxin were recommended.

The pharmacokinetics, protein binding, excretion and tissue distribution of 67Ga after the administration of 67Ga-citrate to New Zealand White rabbits is described. Data for 67Ga blood levels were best described by an equation with three exponential components exhibiting half lives of 0.25 h, 7.4 h and 19.5 h, with almost all of the activity in a protein bound form. Weekly urinary excretion (approximately 27%), possibly in a metabolized form, and fecal elimination (approximately 20%) were greater than the reported values in man, but there was a similar organ distribution pattern in these animals as in man. The overall biological handling was judged to be similar in both species making the rabbit a suitable model for further 67Ga-citrate studies in vivo.

The vasodilative effects associated with the use of sodium acetate have been reported in the literature. Preparations of plasma protein fraction (PPF) substantially free of this vasodilator were developed. This paper presents and discusses experimental work on the improved product.