Irritable Bowel Syndrome (IBS) is a common and debilitating disease with few effective treatments. A new study has found that a nonabsorbable antibiotic — one that stays in the gut — can be an effective long-term treatment for irritable bowel syndrome (IBS), a disease affecting more than 20 percent of Americans.

The study found that antibiotics are more effective if continued for a long time, supporting previous research that pointed to bacterial overgrowth as a cause of the disease.

The study involved 87 participants, all of whom had IBS. They received 400 mg of the antibiotic rifaximin three times a day for 10 days or a placebo. Participants completed an extensive symptom questionnaire measuring the severity of nine symptoms (abdominal pain, diarrhea, constipation, bloating, urgency, incomplete evacuation, mucus, sense of incomplete evacuation and gas).

Researchers found that the rifaximin not only led to significant improvement in IBS symptoms during the 10 days it was administered, but also that the benefit continued for 10 weeks afterward.

"The fact that the benefit of the targeted antibiotic continued even after it was stopped provides evidence that the antibiotic was acting on a source of the problem: excess bacteria in the gut," said Mark Pimentel, M.D., director of the GI Motility Program at Cedars-Sinai and the study's principal investigator."This finding offers a new treatment approach — and a new hope — for people with IBS."

Irritable Bowel Syndrome is one of the ten most frequently diagnosed conditions by U.S. physicians. It is an intestinal disorder that causes abdominal pain, cramping, bloating and diarrhea and/or constipation and is a long-term condition that usually begins in early adult life. IBS is more common in women than in men.

The study appears in the October 17, 2006 issue of the Annals of Internal Medicine. "While this study being released today demonstrates that the non-absorbed antibiotic rifaximin has great promise in the clinical improvement of IBS, more research is needed," said Pimentel. "Next steps include multi-center studies to further assess short- and long-term benefits of this drug. Tests comparing rifaximin to other types of antibiotics that have been used to treat the disease should also be conducted."