Rifaximin Offers Symptom Relief for IBS Without Constipation

Abstract

A pair of clinical trials has found that 2 weeks of treatment with the minimally absorbed antibiotic, rifaximin, provides significant relief of irritable bowel syndrome (IBS) symptoms. In addition, the studies found that the benefits of treatment with rifaximin persisted for 10 weeks after patients stopped taking the antibiotic, said Yehuda Ringel, MD, Associate Professor of Medicine in the University of North Carolina School of Medicine and a co-author of the studies, which were published in the January 6, 2011, issue of The New England Journal of Medicine. “These results support the idea that intestinal microbiota may be an underlying cause of IBS, and altering gut bacteria by treatment with rifaximin appears to be an effective way of providing relief to those who suffer from IBS symptoms,” Dr Ringel says. Patients in the study reported relief of their symptoms that extended for weeks after completing treatment with rifaximin. Specifically, they reported relief from bloating, less abdominal pain, and improved stool consistency for up to 10 weeks. Although the concept of bacteria playing a key role in IBS pathophysiology was controversial when first unveiled a decade ago, research confirms that gut flora trigger IBS symptoms. The findings also show that targeted antibiotics provide safe, effective, long-lasting relief for this condition, said Mark Pimentel, MD, GI Motility Program director and principal investigator of the clinical trial at Cedars–Sinai Medical Center in Los Angeles. The 2 studies, known as TARGET 1 and TARGET 2, were conducted in parallel from June 2008 through June 2009. In the studies, a total of 1260 patients who had IBS without constipation were enrolled at one of 179 study sites in the United States and Canada. All were randomized to receive the study drug in 550-mg doses, 3 times daily for 2 weeks, or placebo. All were then followed for an additional 10 weeks. Adequate relief was defined as self-reported relief of symptoms for ≥2 of the first 4 weeks after treatment. Other secondary end points included the percentage of patients who had a response to treatment as assessed by daily self-ratings of global IBS symptoms and individual symptoms of bloating, abdominal pain, and stool consistency during the 4 weeks after treatment and during the entire 3 months of the study. Significantly more patients in the rifaximin group than in the placebo group had adequate relief of global IBS symptoms during the first 4 weeks after treatment (40.8% vs 31.2% [P = .01], in TARGET 1; 40.6% vs 32.2% [P = .03] in TARGET 2; and 40.7% vs 31.7% [P < .001] in the 2 studies combined). Similarly, more patients in the rifaximin group than in the placebo group had adequate relief of bloating (39.5% vs 28.7% [P = .005] in TARGET 1; 41.0% vs 31.9% [P = .02], in TARGET 2; and 40.2% vs 30.3% [P < .001] in the 2 studies combined) and significantly more patients in the rifaximin group had a response to treatment as assessed by daily ratings of IBS symptoms, bloating, abdominal pain, and stool consistency. The incidence of adverse events was similar in the 2 groups. The studies concluded that 550-mg doses of rifaximin taken 3 times a day for 14 days provides better relief of IBS symptoms than placebo for up to 10 weeks after completion of therapy. “These studies support the idea that gut bacteria have an important role in maintaining normal intestinal function and emphasize the need for further research on the interaction between the intestinal microbiota and the human host,” Dr Ringel says.