Study: Acetylcysteine ineffective against contrast-induced nephropathy

Drug Thought To Protect Kidneys From Imaging Dye Doesn't Work
17 Nov 2010

An oral drug given to protect the kidneys from contrast dye didn't reduce the risk of kidney damage, according to a late-breaking clinical trial presented at the American Heart Association's Scientific Sessions 2010.

The new data that acetylcysteine doesn't protect the kidneys from the potential for damage from this dye may change the way patients are treated, said Otavio Berwanger, M.D. Ph.D., lead author of the study and director of the Research Institute at the Hospital do Coração in Sao Paulo, Brazil.

Contrast dye is used during coronary arteriograms and angiography procedures, which include diagnostic X-rays of the heart's blood vessels, as well as in x-rays of other blood vessels. The dye may adversely affect kidney function in some patients, especially those older than 70 years and who have had previous kidney failure, congestive heart failure or diabetes.

In previous smaller studies, researchers found mixed results regarding the benefits of using acetylcysteine to minimize kidney damage from the contrast dye. Because of positive results from some studies, acetylcysteine - a cheap, relatively safe drug - has been used to shield the kidneys from the contrast dye.

"This will inform clinical practice, of course," he said. "A negative study is just as important as a positive study. Sometimes you have something implemented in clinical practice that is not useful, even if it is safe and cheap."

It's not clear why the contrast dye harms some patients' kidneys. The damage is often reversible, but in some patients it can result in the need for dialysis or cause death. The highest risk for problems occurs in the first three days after the exam.

"The heart and kidneys are connected," Berwanger said. "Some patients need this type of exam to diagnose if they need revascularization, but it's not good enough to fix the heart if it harms the kidneys."

In the trial, researchers examined 2,308 patients from 46 centers in Brazil. The study ended sooner than expected because doctors enrolled patients at a faster rate than expected.

Researchers randomly assigned patients to receive acetylcysteine or a placebo before and after the cardiac X-ray procedure. Researchers looked for signs of contrast-induced kidney damage, the second most common cause of hospital kidney failure in Brazil and the third leading cause of kidney failure in hospitals in the United States.

About 75 percent of patients were given a low-osmolar dye, which is more protective for the kidneys than high-osmolar agents. Iso-osmolar dye was used in about 3 percent of the patients. There were no differences between the acetylcysteine and placebo groups as to the types of dyes patients received.

Patients who received acetylcysteine had the same incidence of kidney damage - 13 percent - as those who took the placebo.

Because of the study's negative results, Berwanger said the next step is to find either a contrast dye that's less toxic to the kidneys or something else that can protect the kidney from the dye.

"A lot of research needs to be done," he said. "We have different types of contrast and the newer types claim to be less toxic to the kidney. But we don't know which new one to choose. We need to use contrast, so we need to give patients the best and the safest."

In an upcoming study of 4,800 patients in Brazil and other South American countries, this group of researchers will explore saline to protect the kidneys, which has been used in some hospitals. They are also in the early stages of examining bicarbonate.

"The ACT II trial is already in the planning phase," Berwanger said. "We're comparing bicarbonate to normal saline and comparing to different types of contrast."

Co-authors are Amanda G.M.R. Sousa, M.D., Ph.D.; Alexandre B. Cavalcanti, M.D., Ph.D.; Anna M. Buehler, M.D., Ph.D.; Mariana T. Carballo, M.A.; Jose E. M. R. Sousa, M.D., Ph.D. and Alessandra A. Kodama, M.A. Author disclosures are on the abstract.

The Ministry of Health in Brazil funded the study.

Source:
American Heart Association

Article URL: http://www.medicalnewstoday.com/articles/208139.php

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My take:

Note also that the reported incidence of kidney damage--13% with or without acetylcysteine--is much higher than the 3% figure that was quoted in previous studies (and that I had cited in a few of my posts).
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