But for some, nothing much works, and IBS can leave them unable to work, attend social events or even travel short distances.
Prior research has suggested that an imbalance in gut flora, or bacteria that live in the small intestine and colon, might contribute to IBS.
The fact that an antibiotic, which kills bacteria, was effective supports that, Ringel said.
But there is much still to learn. Experts don't know if an alteration of the microflora causes the condition or, perhaps, is a result of the condition, Ringel said.
And rifaximin is a broad-spectrum antibiotic, meaning it kills lots of types of bacteria, Tack said. Researchers also don't know which bacteria might contribute to IBS.
"And right now we only have 12 weeks of data," Tack said. "What happens if you relapse? Can you treat them again with rifaximin, and will it work?"
The U.S. National Digestive Diseases Information Clearinghouse has more on irritable bowel syndrome.
SOURCES: Yehuda Ringel, M.D., associate professor, medicine, division of gastroenterology and hepatology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, N.C.; Jan Tack, M.D., Ph.D., professor, medicine, Translational Research Center for Gastrointestinal Disorders, University of Leuven, Leuven, Belgium; Jan. 6, 2011, New England Journal of Medicine
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