Gestational age and indomethacin elimination in the neonate.

The disposition of oral indomethacin was studied in 9 premature infants with significant patent ductus arteriosus (sPDA) with birth weights ranging from 800 to 1,960 gm and gestational ages of 28 to 36 wk. Peak plasma concentrations in most of the subjects were not observed until 3 to 4 hr after administration and ranged from 0.027 to 0.31 microgram/ml. Plasma half-life (t1/2) of indomethacin ranged from 11 to 20 hr and correlated with gestational age. Plasma protein binding studies, in samples from the premature infant using radiolabeled indomethacin, showed no difference in binding from values obtained with adult plasma (greater than 98%). Absorption of orally administered indomethacin appears to be incomplete and plasma clearance much longer than in the adult.