PLASMA INDOMETHACIN LEVELS IN PRETERM NEWBORN-INFANTS WITH SYMPTOMATIC PATENT DUCTUS-ARTERIOSUS - CLINICAL AND ECHOCARDIOGRAPHIC ASSESSMENTS OF RESPONSE

In order to close their patent ductus, 50 newborn infants received 65 courses of indomethacin, eitherorally or rectally. There were 33 clinical responses and 32 nonresponses. There was no difference between R and NR groups at the time of Indo therapy for the following: number of days of medical therapy prior to Indo; postnatal or postconceptional age; weight; FiO: decrease in urine output; BUN. The echographic left atrium to aortic ratio decreased in both groups after Indo, showing an echographic effect in the presence of a clinical NR. Plasma Indo concentration was measured in 41 infants by a high performance liquid chromatographic assay. The levels obtained were similar to previously published adult and pediatric values. There was no difference between the mean of the highest plasma Indo levels measured in the R group (632±385 ng/ml) vs the NR group (505±243 ng/ml). There was no relation between the Indo level and either postnatal or postconceptional age. Indo concentrations remained elevated when compared with values in adults; this may be related to enterohepatic recirculation in concert with immature renal or hepatic function. Poor absorption of Indo does not account for failure of the ductus to close in symptomatic preterm neonates. © 1979 The C. V. Mosby Company.