intravenously. In addition, studies could be done in individuals without cardiovascular risk factors to determine whether the effectiveness of statin therapy in reducing CIN occurs in the absence of the physiologic effects of statins on coexisting cardiovascular disease. Little evidence exists on the comparative effectiveness of different regimens for giving fluids to patients receiving contrast media, despite the fact that current clinical practice often involves use of oral hydration alone for studies with IV contrast media. If oral hydration were shown to be as effective as IV saline, it would be a simple and potentially cost-effective strategy for preventing CIN. Unfortunately, very few studies investigated oral hydration versus IV saline. Hence, more studies are needed to investigate the effectiveness of oral hydration versus IV saline, especially for intra-arterial contrast procedures such as coronary angiography. Finally, it is very difficult to apply the existing evidence to patients receiving IV contrast media because the vast majority of studies focused on patients receiving intra-arterial contrast media. The risk of CIN may be low enough with the IV administration of LOCM and IOCM to make it very difficult to demonstrate the effectiveness of an intervention for preventing CIN. To determine the effectiveness of interventions for preventing CIN in patients receiving IV contrast media, it may be necessary to perform large studies of patients having a high risk for developing CKD. Regardless of which populations or interventions are involved, it is important that future studies use an accepted definition of CIN and report outcomes beyond CIN that are important to patients. Critical for future studies is more standardized reporting on adverse outcomes, such as drug side effects, need for hemodialysis, length of hospitalization, quality of life, and mortality. To develop more effective interventions for preventing CIN, it may be necessary to conduct additional research on the pathophysiological mechanisms by which contrast media may contribute to acute kidney injury. It would be important to differentiate the direct effects of contrast media from other factors that can contribute to acute kidney injury in patients receiving IV or intra-arterial contrast media. Conclusions From all the studies of interventions to reduce the risk of CIN, the evidence only shows a clinically important and statistically significant benefit in studies of three comparisons: low-dose N-acetylcysteine compared with IV saline, N-acetylcysteine compared with IV saline in patients receiving LOCM, and statins plus N-acetylcysteine compared with N-acetylcysteine alone in patients receiving intra-arterial contrast media. 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