We hypothesize that feeding preterm infants while they receive indomethacin or ibuprofen therapy for treatment of a patent ductus arteriosus will decrease the incidence of feeding intolerance and shorten the time period that infants need to tolerate full enteral nutrition. We also hypothesize that this intervention will minimize the alterations in intestinal permeability that occur with these drugs and will improve the infants' hemodynamic response to enteral nutrition