Multicenter, placebo-controlled randomized trial for prevention of post ERCP pancreatitis with Risperidone

INTERVENTION: Risperidone group is orally administered with 2 capsules filled with 1mg risperidone and lactose 50 to 120 minutes before ERCP. Placebo group is administered orally with 2 capsules filled with lactose 50 to 120 minutes before ERCP. CONDITION: post ERCP pancreatitis PRIMARY OUTCOME: The primary endpoints are frequency and severity of post ERCP pancreatitis. ; Post ERCP pancreatitis is defined according to Consensus Guideline (by Cotton Classification) published in 1991 as follows.; 1)Serum amylase level that is three times higher than normal upper limit. ; 2)Abdominal pain persisting for at least 24 hours. SECONDARY OUTCOME: 1) Change in serum amylase, pancreatic amylase, and lipase ; 2) The incidence of abdominal pain and hyperenzymemia. INCLUSION CRITERIA: Patients who are planned to undergo first ERCP. Written informed consent is obtained from patient before the study.