Before birth, blood pumped from the heart through the pulmonary artery toward the lungs is shunted into the aorta. This arterial shunt is a short vessel called the ductus arteriosus. When the shunt is open, it is said to be patent.
The ductus arteriosus usually closes at or shortly after birth, permitting blood from that moment on to course from the heart directly to the lungs. However, if the ductus arteriosus remains open (patent), flow reverses and blood from the aorta is shunted left-to-right into the pulmonary artery and thence recirculated through the lungs.
PDA is a particularly common problem in premature infants with the respiratory distress syndrome (RDS). The left-to-right shunt through the ductus increases their risk of serious complications including brain hemorrhage. IV indomethacin (Indocin) was the conventional therapy to promote closure of PDA in premies but indomethacin affects blood flow to organs such as the kidney and can lead to complications like renal failure. Ibuprofen (the active ingredient in Advil, Motrin, Medipren and Nuprin) has been found to work as well as indomethacin in treating PDA in preterm infants with the respiratory distress syndrome and is less likely to impair their kidney function.