AIM:To investigate the efficacy and adverse effects of antioxidant therapy in acute pancreatitis(AP),chronic pancreatitis(CP) and post-endoscopic retrograde cholangiopancreatography pancreatitis(PEP).METHODS:Pub Med,Scopus,Google Scholar,Cochrane library database,and Evidence-based medicine/clinical trials published before August 2014 were searched. Clinical and laboratory outcomes of randomized trials of antioxidant therapy in patients with AP,CP and PEP were included. The methodological quality of the trials was assessed by the Jadad score based on the description of randomization,blinding,and dropouts(withdrawals). The results of the studies were pooled and meta-analyzed to provide estimates of the efficacy of antioxidant therapy.RESULTS:Thirty four trials out of 1069 potentially relevant studies with data for 4898 patients wereeligible for inclusion. Antioxidant therapy significantly reduced the length of hospital stay in AP patients {mean difference-2.59 d(95%CI:-4.25-(-0.93)],P = 0.002}. Although,antioxidant therapy had no significant effect on serum C reactive protein(CRP) after 5-7 d in AP patients [mean difference-9.57(95%CI:-40.61-21.48,P = 0.55],it significantly reduced serum CRP after 10 d {mean difference-45.16 [95%CI:-89.99-(-0.33)],P = 0.048}. In addition,antioxidant therapy had no significant effect on CP-induced pain [mean difference-2.13(95%CI:-5.87-1.6),P = 0.26]. Antioxidant therapy had no significant effects on the incidence of all types of PEP [mean difference 1.05(95%CI:0.74-1.5),P = 0.78],severe PEP [mean difference 0.92(95%CI:0.43-1.97),P = 0.83],moderate PEP [mean difference 0.82(95%CI:0.54-1.23),P = 0.33],and mild PEP [mean difference 1.33(95%CI:0.99-1.78),P = 0.06]. Furthermore,while antioxidant therapy had no significant effect on serum amylase after less than 8 h sampling [mean difference-20.61(95%CI:-143.61-102.39),P = 0.74],it significantly reduced serum amylase close to 24-h sampling {mean difference-16.13 [95%CI:-22.98-(-9.28)],P < 0.0001}.CONCLUSION:While there is some evidence to support antioxidant therapy in AP,its effect on CP and PEP is still controversial. AIM: To investigate the efficacy and adverse effects of antioxidant therapy in acute pancreatitis (AP), chronic pancreatitis (CP) and post-endoscopic retrograde cholangiopancreatography pancreatitis (PEP). METHODS: Pub Med, Scopus, Google Scholar, Cochrane database database, and Clinical and laboratory outcomes of randomized trials of antioxidant therapy in patients with AP, CP and PEP were included. The methodological quality of the trials was assessed by the Jadad score based on the description of randomization, blinding, and dropouts (withdrawals). The results of the studies were pooled and meta-analyzed to provide estimates of the efficacy of antioxidant therapy .RESULTS: Thirty four trials out of 1069 potentially relevant studies with data for 4898 patients wereeligible for inclusion. Antioxidant therapy significantly reduced the length of hospital stay in AP patients {mean difference-2.59 d (95% CI: -4.25 - (- 0.93)], P = 0.002}. Although antioxidant therapy had no significant effect on serum C reactive protein (CRP) after 5-7 days in AP patients [mean difference-9.57 (95% CI: -40.61-21.48, P = 0.55] serum CRP after 10 d {mean difference-45.16 [95% CI: -89.99 - (-0.33)], P = 0.048} % CI: -5.87-1.6), P = 0.26]. Antioxidant therapy had no significant effects on the incidence of all types of PEP [mean difference 1.05 (95% CI: 0.74-1.5), P = 0.78], severe PEP [ Mean PEP [mean difference 0.92 (95% CI: 0.43-1.97), P = 0.83], moderate PEP [mean difference 0.82 : 0.99-1.78), P = 0.06]. Furthermore, while antioxidant therapy had no significant effect on serum amylase after less than 8 h sampling [mean difference-20.61 (95% CI: -143.61-102.39), P = 0.74] it significantly reduced serum amylase close to 24-h sampling {mean difference-16.13 [95% CI: -22.98 - (- 9.28)], P <0.0001}. CONCLUSION: While there some some evidence to support antioxidant therapy in AP, its effect on CP and PEP is still controversial.