Rifaximin Successfully Relieves IBS


Patients suffering from irritable bowel syndrome (IBS) with symptoms such as diarrhea may harbor some harmful bacteria and other microorganisms. This study was conducted to examine the effectiveness of the antibiotic rifaximin that is not absorbed by the intestines, but can function against the microorganisms in the gut. For the study, rifaximin was compared with placebo. The researchers concluded, “Among patients who had IBS without constipation, treatment with rifaximin for two weeks provided significant relief of IBS symptoms, bloating, abdominal pain, and loose or watery stools.”


The hallmarks of IBS are recurring symptoms of abdominal pain, bloating and altered bowel function and have no definite inflammation or other abnormalities. This is one of the reasons why this condition fails to respond to therapy like dietary and lifestyle modifications, fiber supplementation, psychological therapy and even medications. Rifaximin is an antibiotic that is active against a wide range of microbes without being absorbed in the intestine. Earlier smaller studies have shown that rifaximin aids in killing some harmful bacterial growth in an IBS patient’s gut. This study was conducted on a larger scale to see if the same findings were observed.


  • There were two large studies – Target 1 and Target 2. These studies involved , patients (Target 1: 623 and Target 2: 637). These patients had IBS symptoms without constipation.
  • Patients received 550 mg of rifaximin or a placebo in two groups that were selected randomly. The medication or placebo was given three times daily for two weeks. Thereafter the patients were followed up for 10 more weeks.
  • All participants were asked to report if they had relief from bloating, pain, bowel inconsistency and other symptoms.


  • Adequate relief of all symptoms of IBS was seen in 40.7 percent on rifaximin (statistically significantly higher) compared to 31.7 percent on placebo.
  • Response to therapy was also significantly higher with rifaximin (40.2 percent) compared to placebo (29.5 percent).
  • 40.3 percent patients on rifaximin perceived their abdominal bloating reduced compared to 30.3 percent on placebo. Both pain and loose stools were decreased with rifaximin compared to placebo (46.6 percent with rifaximin compared to 38.5 percent with placebo in Target 1; 46.7 percent with rifaximin compared to 36.3 percent with placebo in Target 2).
  • Rifaximin showed sustained relief over the three months of the study.

Shortcomings/next steps

Authors admit that some patients on rifaximin did not respond to treatment, which may indicate a difference in the root cause of IBS-like symptoms. This may suggest that the underlying mechanism of the disease is not well understood. Also, the exact mechanism by which rifaximin acts in relation to IBS is still unknown. This could be explored in future studies.


To conclude, “the results of these two phase 3 studies showed that treatment with rifaximin at a dose of 550mg three times daily for 14 days provides better relief of symptoms of IBS than does placebo for up to 10 weeks after completion of therapy.” Many patients suffering from this condition are most unresponsive to conventional therapy, including psychological therapy, fiber supplementation, lifestyle and diet changes and drug therapy. This study may possibly help develop a new therapy for IBS patients. Although the effectiveness is not seen in all patients, rifaximin may be recommended for IBS patients without constipation.

For More Information:

Rifaximin Therapy for Patients with Irritable Bowel Syndrome without Constipation

Publication Journal: The New England Journal of Medicine, January 2011

By Mark Pimentel, MD; Anthony Lembo, MD

From the Cedars–Sinai Medical Center, Los Angeles, the Beth Israel Deaconess Medical Center, Boston, Massachusetts, and the Harvard Medical School,  Boston, Massachusetts

*FYI Living Lab Reports Are Summaries of the Original Research.
Tags from the story