Pharmacokinetics and Echocardiographic Effects of Digoxin in Low Birth Weight Infants with Left-to-Right Shunting due to Patent Ductus arteriosus

Abstract

Serum digoxin (DIG) levels, timed urine and M-mode echocardiograms were performed in 9 low birth weight infants with lef't-to-right shunting due to patent ductus arteriosus treated with DIG (40 μg/kg in 3 and 20 μg/kg in 6). Half the DIG was given initially and a quarter at 8-hourly intervals. Serum DIG levels at 24 h (1.8-7 .0 ng/ml) were similar in both dose groups. One infant in the 40 μg/kg dose group developed Wenckebach phenomenon. Left atrial to aortic root ratio feil within 30 min and remained reduced during the ensuing 24 h (p < 0.025). There were no significant changes in the other echocardiographic measurements. Half-life of distribution and elimination of DIG were 1.04 ± 0.46 and 15.25 ± 0.36 h. The α-phase volumes of distribution (VD) differed between the 40 and 20 μg/kg dose groups (2.28 ± 0.05 vs. 1.33 ± 0.66 liters/kg, p < 0.025). The β-phase VD (4.25 ± 0.61 and 2.76 ± 0.99, respectively) were similar. Mean urinary DIG clearance was 13.1 ± 3.2 ml/min/1.73^2.