The results of a meta-analysis published in the February 19, 2008 issue of the Annals of Internal Medicine found that N-acetylcysteine works better than other agents to help prevent kidney damage (nephropathy) caused by iodine-containing dyes known as contrast agents which are used to enhance the visualization of organs or other structures during CT scans, angiograms and other imaging scans. Contrast-induced nephropathy is diagnosed when blood creatinine, an indicator of kidney function, increases 25 percent or more within 48 hours following contrast agent administration.
For the review, Aine Kelly, MD, MS, and her University of Michigan colleagues selected 41 randomized, controlled trials that compared the protective ability of a control agent such as saline to N-acetylcysteine, theophylline, fenoldopam, dopamine, iloprost, statin, furosemide, or mannitol in a group of patients in which intravenous iodinated contrast agents were used. The analysis did not include studies involving non-iodinated contrast agents such as barium or gadolinium.
Of the agents analyzed, only N-acetylcysteine was clearly shown to help prevent contrast-induced nephropathy. Although theophylline was found to reduce nephropathy risk more than saline, the amount was not enough to be considered significant. One drug, furosemide, actually increased kidney damage risk.
Elderly individuals and those with diabetes or heart failure have the greatest risk of experiencing contrast-induced nephropathy, and could benefit the most from prophylactic N-acetylcysteine use. Mild to moderate kidney damage occurs following CT scans in one in four of these high-risk individuals. Even among those with normal kidney function, an estimated one in ten experiences some kidney damage from the use of these contrast agents. Dr Kelly recommended that men and women with impaired kidney function speak up when their physician orders a CT scan or angiogram to ensure that they are given an N-acetylcysteine tablet beforehand. Healthy individuals may wish to request that their blood creatinine levels be tested prior to undergoing these scans, in order to ascertain whether they have any unknown kidney impairment.
“Millions of people receive contrast agent each year, including most heart patients who have angioplasties and stents, as well as those having a CT scan. Contrast agent helps physicians see the things we need to see, but it also does pose a hazard to some people,” Dr Kelly stated. “This drug, which is quick, convenient, inexpensive and widely available, with no major side effects, appears to be the best choice to protect those whose kidneys are most at risk.”