The drug, N-acetylcysteine, can prevent serious kidney damage that can be caused by the iodine-containing "dyes," or contrast agent, doctors use to enhance the quality of such computed tomography scans. The contrast agent is usually given intravenously before a CT scan, angiogram or other test.

University of Michigan Health System researchers performed a meta-analysis of 41 randomized controlled studies that evaluated various drugs for their kidney-protecting effects.

Study leader Dr. Aine Kelly said only N-acetylcysteine clearly prevented contrast-induced nephropathy -- the medical name for kidney damage caused by contrast agents. The drug Theophylline was believed to a possible kidney-protecting agent, but it did not reduce risk significantly, Kelly said. Other drugs had no effect, and one, furosemide, raised kidney risk.

The study, published in the Annals of Internal Medicine, showed that taking N-acetylcysteine before receiving the contrast agent can protect patients from kidney damage -- and that it works better than other medicines that have been proposed for the same purpose.