Am Fam Physician. 2011 Dec 1;84(11):1292-1293.
Background: Irritable bowel syndrome (IBS) is a gastrointestinal disorder that is characterized by bloating, abdominal pain, and changes in stool frequency and/or consistency. For many patients, IBS-related symptoms are not alleviated by the current treatments available. Some evidence suggests that changes in the bowel microbiota of patients with IBS may play a role in the pathophysiology. Systemic antibiotics have shown inconsistent results for symptomatic relief in patients with IBS, but a nonsystemic antibiotic, such as rifaximin (Xifaxan), could allow a targeted therapy for reduction or alleviation of IBS symptoms. Pimentel and colleagues investigated rifaximin as an effective treatment for the alleviation of bloating, abdominal pain, and loose stools in patients who had IBS without constipation.
The Study: The authors evaluated two randomized placebo-controlled trials (TARGET 1 and TARGET 2) of patients who had IBS without constipation. Patients were randomized to receive 550 mg of rifaximin or placebo three times per day for two weeks. Symptoms were recorded for an additional 10 weeks after treatment ended. Study end points were the percentage of patients with adequate relief (for at least two of the first four weeks after treatment) of global IBS symptoms, bloating, abdominal pain, and loose stools. Patients were asked to rate the average daily amounts of abdominal pain and bloating, and the average daily stool consistency.
Results: In both trials, significantly more patients in the rifaximin group (40.7 versus 31.7 percent in the placebo group) experienced adequate relief of global IBS symptoms during the first month after treatment. Significantly more patients treated with rifaximin self-reported adequate relief of bloating in both trials (40.2 versus 30.3 percent for placebo). In addition, patients receiving rifaximin self-reported significant improvement in abdominal pain and stool consistency compared with placebo. There were no significant differences in the rates of infections or other adverse events between groups.
Conclusion: Patients who have IBS without constipation experience significant relief of global IBS symptoms, abdominal pain, bloating, and loose stools after two weeks of treatment with 550 mg of oral rifaximin, three times per day.
Pimentel M, et al. Rifaximin therapy for patients with irritable bowel syndrome without constipation. N Engl J Med. January 6, 2011;364(1):22–32.
editor's note: Few pharmacologic treatments have proved effective in providing symptomatic relief of IBS. The relative ineffectiveness of most treatments could be attributed to an etiology that is most likely heterogenous.1 Some studies suggest that alterations in the normal gut flora could be a significant contributor to the pathogenesis of IBS.2 Earlier studies have shown inconsistent results with poorly absorbed antibiotics for symptom alleviation in patients with IBS.3 In this study, Pimentel and colleagues provided encouraging evidence for rifaximin use in patients with IBS.
An accompanying editorial notes that although the percentage of patients reporting symptom alleviation compared with placebo (9 to 12 percent more with rifaximin) is statistically significant, it is of modest clinical relevance.4 Additional areas of concern are the chronic nature of IBS and bacterial resistance. Pimentel and colleagues studied a one-time treatment and its effectiveness during a short-term period (10 weeks after the initial two-week treatment phase); it is unclear if symptomatic relief would persist or if retreatment would be equally efficient if required. IBS is a relatively common condition, and widespread rifaximin use has the potential to alter bacterial resistance profiles in the intestinal tract over time. Currently, rifaximin is not approved by the U. S. Food and Drug Administration for the treatment of patients with IBS. More studies evaluating rifaximin as a long-term or intermittent IBS therapy would be useful in assessing the drug's potential as a reliable IBS treatment. Nonetheless, the TARGET 1 and TARGET 2 short-term trials have provided optimism for rifaximin as an effective IBS treatment, and it should be added to the list of other IBS therapies currently available.—B.M. and SUMI SEXTON, MD, Associate Editor, American Family Physician
1. Longstreth GF, Thompson WG, Chey WD, Houghton LA, Mearin F, Spiller RC. Functional bowel disorders [published correction appears in Gastroenterology. 2006;131(2):688]. Gastroenterology. 2006;130(5):1480–1491.
2. Lee KJ, Tack J. Altered intestinal microbiota in irritable bowel syndrome. Neurogastroenterol Motil. 2010;22(5):493–498.
3. Pimentel M, Park S, Mirocha J, Kane SV, Kong Y. The effect of a nonabsorbed oral antibiotic (rifaximin) on the symptoms of the irritable bowel syndrome: a randomized trial. Ann Intern Med. 2006;145(8):557–563.
4. Tack J. Antibiotic therapy for the irritable bowel syndrome. N Engl J Med. 2011;364(1):81–82.
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