Indomethacin therapy in infants with advanced postnatal age and patent ductus arteriosus.

A trial of intravenous indomethacin therapy was performed on 11 premature infants whose postnatal age was 8 weeks or more (mean 65.3 days). In an attempt to maintain the desired plasma level, indomethacin was given at a dosage of 0.3 mg/kg, at 8-hour intervals (total dose 0.9 mg/kg) for a total of 3 doses. In spite of desirable plasma indomethacin levels (which ranged from 280-870 ng/ml) and area under the curve (24.1 micrograms/hr/ml), calculated from time 0 to 24 hrs after the initial dose, none of the infants responded to indomethacin with ductus closure. There were a transient significant decrease in urine output, creatinine clearance, and fractional excretion of sodium. The present study confirms the clinical impression that Indomethacin is ineffective for the closure of ductus arteriosus in infants with advanced postnatal age.