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Rifaximin Stops IBS Symptoms up to 10 Weeks

Kathleen Blanchard's picture

Researchers find the antibiotic rifaximin relieves irritable bowel syndrome (IBS) for weeks. In a study published in the New England Journal of Medicine, the antibiotic was found to relieve symptoms of IBS for weeks after stopping the drug. Patients given the medication reported less bloating, abdominal pain and relief from loose, water stools for up to 10 weeks, after receiving two weeks of rifaximin therapy.

Gut bacteria play a key role in IBS symptoms

The study authors say the findings confirm that bacteria in the gut play a key role in the development of irritable bowel syndrome. Mark Pimentel, M.D., GI Motility Program director and principal investigator of the clinical trials at Cedars-Sinai where the study was conducted says, “For years, the treatment options for IBS patients have been extremely limited."

Rifaximin is unique because it stays in the gut and is only minimally absorbed into the bloodstream. In the study of over 600 patients who were given the medication or a placebo, 40.7 percent taking rifaximin reported relief of IBS symptoms that endured for weeks after the medication was stopped.

The researchers conducted two identical phase 3, double-blind, placebo-controlled trials (TARGET 1 and TARGET 2) that included weekly self assessments of symptom relief of as a primary end-point and bloating as a secondary outcome.

Pimentel explains the study shows bacterial flora in the stomach and intestines play a role in the disease because “IBS often does not respond well to treatments currently available... With this antibiotic treatment, the patients feel better, and they continue to feel better after stopping the drug. This means that we did something to strike at the cause of the disease.”

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Patients with IBS typically experience diarrhea, constipation or a mixture of both. Bloating, abdominal pain, gas and cramping are prevalent. The antibiotic treatment seems to target the cause of the irritable bowel syndrome rather than treating the symptoms.

In the study, the scientists looked at the antibiotic's effect on patients with IBS and predominantly diarrhea.

Past studies from the research group found a link between IBS symptoms and bacterial fermentation in the gut when bacterial become overly abundant in the small intestine, leading them to explore the antibiotic treatment.

Patients received rifaximin 550 milligram, or placebo three times a day for two weeks. Those given placebo experienced a 30.3 percent reduction in IBS symptoms, compared to the 40.7 percent given the antibiotic treatment. Compared to placebo that reduced 28.7 percent of bloating among the study participants, just 39.5 percent of the group experienced relief.

The drug is not yet approved by the FDA for treating irritable bowel syndrome. Rifaximin is manufactured by Salix pharmaceuticals that funded the study. Dr. Pimentel is a member of their advisory board and a consultant for the drug company.

The cause of irritable bowel syndrome has eluded researchers. The findings that the antibiotic provided symptomatic relief to study participants coud mean improved treatment option for IBS sufferers, should rifaximin meet approval from the FDA.

N Engl J Med 2011; 364:22-32January 6, 2011