Rifaximin Shows Promise in Treating Patients With IBS

Researchers found an 11% treatment effect in patients with irritable bowel syndrome (IBS) taking rifaximin (Xifaxan) for 2 weeks; 40% of patients receiving the medication reported adequate relief of symptoms.

About Irritable Bowel Syndrome (IBS)

Patients with IBS suffer from recurring symptoms of abdominal pain, bloating, and altered bowel function in the absence of structural, inflammatory, or biochemical abnormalities. Treatment options include dietary and lifestyle modifications, fiber supplementation, psychological therapy, and pharmacotherapy, but often patients do not report adequate relief. Disruption in intestinal microbiota has led researchers to consider treating patients with neomycin therapy and systemic antibiotics, but results have been marginal to mixed and adverse effects may limit their use.

Dr Mark Pimentel, Cedars-Sinai Medical Center in Los Angeles, and colleagues conducted 2 identical, multisite studies. In total, 1260 patients aged 18 years or older with IBS who were currently experiencing symptoms were enrolled in the study; patients with constipation-predominant symptoms were excluded.

Patients were randomized to receive placebo or rifaximin at a dose of 550 mg 3 times daily for 14 days. The brand of rifaximin, Xifaxan, is manufactured by Salix Pharmaceuticals, which provided support for this study. After completion of the placebo or rifaximin course, patients were followed for 10 additional weeks. During that time, patients were assessed by periodic study visits and daily via telephone and interactive voice-response system.

Overall, significantly more patients receiving rifaximin than placebo reported adequate relief of global IBS symptoms for at least 2 of the first 4 weeks after treatment (40.7% versus 31.7%, P < 0.001). Patients in the rifaximin group also noted improvement in specific symptom areas of IBS as compared to those patients in the placebo group; these findings were statistically significant. Relief was noted for IBS-related bloating, abdominal pain, and loose or watery stools.

Most important, patients reported the relief continued after treatment. "[With] every other drug that has been used for IBS, once you stop, the symptoms start right back up," Pimentel told the press. "With this one, the patient has lasting benefits."

The safety profile of rifaximin was similar to that of the placebo, with serious adverse events reported in 10 and 15 patients receiving rifaximin and placebo, respectively. The most common adverse events among both groups included headache (6.1% and 6.6% of the rifaximin and placebo groups, respectively), upper-respiratory tract infection (5.6% and 6.2%), and abdominal pain (4.6% and 5.5%).

About Rifaximin

Rifaximin is an antibiotic oral tablet that is currently being used to treat traveler's diarrhea. Rifaximin is a nonaminoglycoside semisynthetic, nonsystemic antibiotic that has been shown to target the gut and is associated with a low risk of bacterial resistance.

"This is the culmination of a 10-year journey in proving that gut bacteria are a cause of IBS," Pimentel said. He and his colleagues are now working on a trial with patients who have IBS and issues with constipation. They hope to have results in about a year's time.

References:

More Information

PubMed Health: Rifaximin

National Institute of Diabetes and Digestive Diseases Information Clearinghouse: Irritable Bowel Syndrome

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Sources

Pimentel M, Lembo A, Chey WD, et al. Rifaximin therapy for patients with irritable bowel syndrome without constipation. N Engl J Med. 2011;364:22-32. http://www.nejm.org/doi/pdf/10.1056/NEJMoa1004409. Accessed January 19, 2011.

Maugh II TH. Antibiotic effective in treating irritable bowel syndrome, study finds. LA Times. http://articles.latimes.com/2011/jan/06/health/la-he-ibs-antibiotic-20110106. Published January 6, 2011. Accessed January 19, 2011.