The present study was undertaken to evaluate if allopurinol administration protects mice from bowel necrosis caused by temporary intestinal ischemia followed by indomethacin (INDO). We have previously reported that ischemia (15-minute occlusion of superior mesenteric vessels) followed by intravenous (i.v.) INDO caused significant bowel necrosis in CD-1 mice. Ischemia or INDO alone did not cause necrosis. To investigate protective measures against necrosis, we used CD-1 mice, 25 to 30 g. Forty-four animals were gavage fed 1 mL of water for 7 days and 32 animals were gavage fed 10 mg/kg allopurinol for 7 days. On the seventh day all animals were anesthetized and the superior mesenteric vessels occluded for 15 to 20 minutes, followed by i.v. INDO (0.5 mg/kg) once daily for 3 days. Animals who died were examined for bowel necrosis and all animals were killed 7 days after surgery and necropsied. Of the 44 saline-fed animals, 12 developed bowel necrosis (27%). Of the 32 allopurinol-fed animals, 1 developed necrosis (3%). The result of Fisher's exact two-tailed test was P = .006. Pretreatment with oral allopurinol significantly protects the mice from developing bowel necrosis when the mesenteric vessels are temporarily occluded and INDO is administered. Allopurinol may prevent reperfusion injury by inhibiting formation of xanthine oxidase generated, oxygen-derived free radicals and may be valuable in pretreating premature infants with patent ductus arteriosus who have had an ischemic episode in whom INDO use is contemplated.