Does Allopurinol Prevent Post Endoscopic Retrograde Cholangio- Pancreatography Pancreatitis? A Randomized Double Blind Trial - Abbasinazari, Mohammad; Mohammad Alizadeh, Amir Houshang; Moshiri, Kamyar; Pourhoseingholi, Mohammad Amin; Zali, Mohammad Reza (Acta Medica Iranica)