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.