Introduction In preterm infants with RDS, PDA contributes to the infiltration and activation of pulmonary neutrophils inducing the secretion of MPO. This enzyme produces hypochloride leading to surfactant inactivation and tissue damage. PDA closure with indomethacin decreases MPO contents of tracheal aspirates. Ibuprofen is a potent anti-inflammatory drug which has been proposed for prophylactic closure of the ductus arteriosus in preterm infants.Aim of the sutdy We investigated whether treatment with ibuprofen, started within 24 hours of age, reduces MPO contents of tracheal aspirates(TA) in preterm infants with RDS. We also studied changes in MPO levels in patients with RDS with spontaneous ductal closure. Method Ten infants of 29±2 weeks' gestational age (GA), 1074±355 grams birth weight(BW), with echocardiographic evidence of PDA and no signs of infection were studied (PDA patients). TA were obtained after instillation of 1ml sterile saline and were frozen at minus 80°C. MPO levels were determined by ELISA. The first sample (MPO1) was collected just before administration of the first dose of ibuprofen (10mg/kg); the second sample (MPO2) was collected at the end of treatment cycle (consisting of two more doses of 5 mg/kg at 24h intervals) after echocardiographical evidence of PDA closure. MPO samples were also collected, at corresponding ages, in 7 intubated infants with RDS of 30±2 w GA, 1150±355 g BW with no evidence of PDA, who were not treated with ibuprofen (non-PDA patients). Table

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Conclusions Pharmacological closure of PDA with iburofen significantly decreases MPO contents of TA in preterm infants. The increase in MPO seen in non-PDA patients after four days of life suggests that the effect of ibuprofen could be due to its anti-inflammatory properties.