Background: Reperfusion injury due to the release of ROS when using CPB and the return of oxygen-rich blood flow to ischemic myocardium after the release of aortic clamps, can cause myocardial dysfunction. Allopurinol as an inhibitor of xanthine oxidase and methylprednisolone is used to reduce the effects of inflammation and reperfusion injury. Method: A double-blind randomized clinical trial study was conducted on 42 patients undergoing coronary artery bypass surgery using CPB between October 2019 and March 2020, which was allocated to the allopurinol group or the methylprednisolone group. Examination of biomarkers of reperfusion injury is carried out by examination of a blood sample of MDA which is performed shortly after the installation of a central venous catheter and 5 minutes after the aortic clamp are removed. MDA examination is done by the ELISA method. Assessment of VIS was carried out in the first 24 hours of postsurgical treatment. While the assessment of the incidence of postoperative arial fibrilation was performed during the first 48 hours after surgery. Results: MDA post reperfusion levels increased significantly in the administration of methylprednisolone (p=0.041) and increased not significantly in the administration of allopurinol (p=0.251). The postoperative VIS value in the administration of allopurinol was significantly lower than in the administration of methylprednisolone (median 6 vs. 22, p = 0.009). The incidence of POAF in the two groups showed no differences were statistically significant (p = 0.231). Conclusion: Allopurinol is more effective than methylprednisolone and can be used in efforts to reduce reperfusion injury in coronary artery bypass surgery. © 2020 Heru Kurniawan, et al.