"Since most of the 470,000 Americans with kidney failure depend on hemodialysis for survival, there is a clear and compelling need to evaluate therapies that reduce or prevent access failure," said NIH Director Elias A. Zerhouni, M.D. "These results tell us we need to keep looking for solutions."

Hemodialysis filters waste and extra fluid from the bloodstream and requires a vascular access -- a site on the body where blood is removed and returned. Fistulas are the preferred type of access since they clot less often, experience fewer infections, and are less costly; patients with fistulas also have lower mortality. A fistula is created by joining a section of an artery and a vein to make one large vessel capable of handling high volumes of blood during hemodialysis. But maintaining any access site is a major clinical challenge. Blood clotting in the fistula is the most frequent cause of early fistula failure. Clotting, infection and low blood-flow rates in the access site are common reasons for hospitalizations requiring multiple treatments or surgeries. Read about vascular access at .

The Dialysis Access Consortium (DAC) found that only 12 percent of patients developed blood clots in the fistula when treated with the clot-preventing drug clopidogrel, compared to nearly 20 percent of patients treated with placebo. Nevertheless, about 60 percent of new fistulas in each group could not be used for long-term dialysis treatments. Complications such as bleeding were similar across the study groups.

DAC studied nearly 900 patients at 9 U.S. medical centers in academic and community practices in urban and rural settings. Participants received a new fistula and took the anti-platelet drug clopidogrel (Plavix) or a placebo tablet daily for 6 weeks to determine if the drug would maintain blood flow in fistulas and increase the number suitable for dialysis.

"Because vascular access is critical for delivering lifesaving care, we are already organizing another multi-center study to look for other ways to improve fistulas," said co-author Catherine M. Meyers, M.D., a kidney specialist in charge of DAC at NIH's National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), which funded the study.

The DAC Fistula Trial is the largest multi-center trial to look at preventing blood clots in new fistulas and the first to test whether prevention would allow more fistulas to be useable for dialysis. NIDDK has funded DAC since 2000. Clopidogrel and placebo were donated by what is now Sanofi Aventis/Bristol-Myers Squibb.

The National Institute of Diabetes and Digestive and Kidney Diseases, a component of the NIH, conducts and supports research in diabetes and other endocrine and metabolic diseases; digestive diseases, nutrition, and obesity; and kidney, urologic, and hematologic diseases. Spanning the full spectrum of medicine and afflicting people of all ages and ethnic groups, these diseases encompass some of the most common, severe, and disabling conditions affecting Americans. For more information about NIDDK and its programs, see .