Patent ductus arteriosus is a postnatal communication, usually between the main pulmonary trunk and the descending thoracic aorta.The clinical consequences of PDA are related to the magnitude of the left-to-right shunt through the PDA with its associated change in blood flow to the lung, kidneys, and intestine, leading to tachypnea, apnea, CO2 retention and increased need to mechanical ventilation. Indomethacin is the only non-selective cyclooxygenase inhibitor approved by FDA for the treatment of PDA. It has been clearly established both by observational studies and randomized trials that indomethacin increases the rate of PDA closure within 24 hours of its administration. Less clearly established are the optimal timing, dose, and duration of treatment.