Researchers at Cedars-Sinai Medical Center have found that a nonabsorbable antibiotic – one that stays in the gut – may be an effective long-term treatment for irritable bowel syndrome (IBS), a disease affecting more than an estimated 20 percent of Americans. The findings, which showed that participants benefited from the antibiotic use even after the course of treatment ended, support previously published research identifying small intestine bacterial overgrowth (SIBO) as a possible cause of the disease.
The research was presented at the recent American College of Gastroenterology's annual meeting in Honolulu, HI.
"This study is important as it is the first to show that the use of targeted antibiotics results in a more significant and long-lasting improvement in IBS symptoms," said Mark Pimentel, M.D., first author on the study and director of the GI Motility Program at Cedars-Sinai. "These results clearly show that antibiotics offer a new treatment approach – and a new hope – for people with IBS."
The randomized, double blind study involved 87 patients. Those on the rifaximin experienced a 37 percent overall improvement of their IBS symptoms as compared to 23 percent on the placebo. Among study subjects whose primary symptom was diarrhea, those on the antibiotic showed more than twice the improvement of those on the placebo (49 percent vs. 23 percent). Patients received the drug (or placebo) for 10 days and were then followed for a total of 10 weeks. Participants kept a stool diary, took a questionnaire and were given methane breath tests. The positive effects of the drug were shown to continue throughout most of the 10-week study, not just during the actual antibiotic course.
Because the cause of IBS has been elusive, treatments for the disease have historically focused on reducing its symptoms – diarrhea and constipation – by giving medications that either slow or speed up the digestive process. In 2000, Pimentel linked bloating, the most common symptom of IBS, to bacterial fermentation, showing that small intestine bacteria overgrowth (SIBO) may be the causative factor in IBS (The American Journal of Gastroenterology, Dec. 2000).
To show evidence of small intestine bacterial overgrowth, participants in both studies were given a lactulose breath test, which monitors the level of hydrogen and methane (the gases emitted by fermented bacteria) on the breath. In the first study, an abnormal breath methane profile was shown to be 100 percent predictive of constipation-predominant IBS. In the current study, the correlation between the amount of methane and the amount of constipation was confirmed, another key finding.
"We were pleased – but not surprised – with the results of this study," said Pimentel. "The next step is to start larger, multi-centered studies to confirm the positive results of this study, which suggest that people can benefit from targeted antibiotic treatment for their IBS."
Irritable Bowel Syndrome is an intestinal disorder that causes abdominal pain or discomfort, cramping or bloating and diarrhea and constipation. It is a long-term condition that usually begins in adolescence or in early adult life. Episodes may be mild or severe and may be exacerbated by stress. It is one of the top ten most frequently diagnosed conditions among U.S. physicians and affects women more often than men.
Other authors from Cedars-Sinai include Sandy Park, B.A., Yuthana Kong M.P.H. and Robert Wade. Sunanda V. Kane from the University of Chicago also participated in the study.
Rifaximin is made by Salix Pharmaceuticals, Inc. Funding for the study was provided by Salix Pharmaceuticals, Inc.
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