Table 2. Principal characteristics of the published randomized studies included in the meta-analysis.

Group	Inclusion criteria	Exclusion criteria	Definition of PEP
Sudhindran[18]	Age >18 years, undergo ERCP	Acute or chronic pancreatitis,use of nitrate-containing medication.	Abdominal or back pain and serum amylase >1000 (normal range 5-300) units⁄ ml 6 and 24 h after ERCP
Wehrmann[19]	Undergo ERCP, papilla was normal	Previous gastroduodenal or bilio-pancreatic surgery or a previous bile-duct cannulation attempt within 3 months before entry into the study. Use of any medication probably affecting SO motility.	Abdominal pain persisting for 24 h associated with a 3-fold increase in serum amylase and⁄ or lipase
Ghori A[20]	Undergo ERCP	Undergo previous sphincterotomy, sent insertion or gastric surgery.	Not clear
Moretó M[21]	Age >18 years, undergo ERCP	Hypersensitivity to nitrates, active acute pancreatitis, anemia, glaucoma, severe hypoxemia with unbalanced ventilation/perfusion , hypotension,Previous sphinterotomy, known tumor of the major duodenal papilla, Use of nitrates, etc.	Abdominal pain persisting for 24 h associated with a 3-fold increase in serum amylase and⁄ or lipase
Talwar A[22]	Age >18 years, undergo ERCP	Previous ERCP resulting in endoscopic sphincterotomy, needle-knife papillotomy, or stenting, Oral or sublingual nitrate use for angina, Patient refusal	Not clear
Kaffes AJ[23]	Age >18 years , with an intact papilla, undergo ERCP	Current nitrate users, hypotensive systolic blood pressure [SBP]<90 mm Hg, hypoxic oxygen saturation [SO2]<95 mm Hg on supplemental oxygen,hemodynamic instability inability to consent, prior adverse effects with nitrate compounds and sildenafil users	Abdominal pain and a greater than 3-fold elevation of serum amylase above the upper limit of normal at 24 hours after the procedure
Beauchant M[24]	Aged between 18 and 75years, undergo ERCP	Acute pancreatitis in the month before inclusion, or chronic pancreatitis or anampullary carcinoma, or if they needed pancreatic sphincterotomy and/or pancreatic stenting, or if their hemodynamic status was unstable, etc.	Epigastric pain and a rise in serum amylase and/or lipase concentration to more than three times the normal upper limit 24 hours after endoscopy
Nøjgaard C[25]	Age >18 years, ERCP procedure planned at the center, patient able to give informed consent	Acute or chronic pancreatitis, sphincterotomy, Hypotension, Anemia, Hypersensibility to GN, Sildenafil administration in the 24 hours before the ERCP procedure, etc	Pain and 3-fold elevated serum amylase
Hao JY[26]	Age >18 years, undergo ERCP	Acute or active chronic pancreatitis, a nitrate allergic history, and those undergone sphincterotomy	Abdominal pain and high-amylase value over the normal value after ERCP. Hyperlipidemia was defined as the higher serum amylase concentration without or only with mild abdominal pain.
Nashaat E[12]	undergo ERCP	Hypersensitivity to used drugs, Active acute pancreatitis, Hypotension, Patients with renal impairment, have peptic ulcer, Patients with previous sphincterotomy, ampullary or pancreatic cancer invading the papilla, ect	Pain and 3-fold elevated serum amylase
Bhatia V[13]	Age>18 years and under a first ERCP	Acute or chronic pancreatitis, lower end malignant bile duct block, ongoing therapy with nitrates, calcium channel blockers, angiotensin-converting enzyme inhibitors, β-blockers, diuretics, or tricyclic antidepressants, patients with angina pectoris , history of myocardial infarction, or cerebral ischemia; and history of allergy to sulfa drugs.	Presence of pain persisting for 24 hours post-ERCP, and associated with a rise in serum amylase levels to more than 3 times the upper limit of normal
Chen XW[14]	Age >18 years, undergo ERCP	Acute or chronic pancreatitis, Hypersensitivity to GTN, sphincterotomy, severe cardiovascular and cerebrovascular diseases, anemia	Abdominal pain persisting for 24 h associated with a 3-fold increase in serum amylase

SO, sphincter of Oddi.