The effect of a nonabsorbed oral antibiotic (rifaximin) on the symptoms of the irritable bowel syndrome: a randomized trial.

BACKGROUND

Alterations in gut flora may be important in the pathophysiology of the irritable bowel syndrome (IBS).

OBJECTIVE

To determine whether the nonabsorbed antibiotic rifaximin is more effective than placebo in reducing symptoms in adults with IBS.

DESIGN

Double-blind, randomized, placebo-controlled study.

SETTING

2 tertiary care medical centers.

PARTICIPANTS

87 patients who met Rome I criteria for IBS and were enrolled from December 2003 to March 2005.

INTERVENTIONS

Participants who met enrollment criteria were randomly assigned to receive 400 mg of rifaximin 3 times daily for 10 days (n = 43) or placebo (n = 44). Eighty participants completed rifaximin therapy or placebo, and follow-up data were available for at least 34 participants per study group at any time point thereafter.

MEASUREMENTS

A questionnaire was administered before treatment and 7 days after treatment. The primary outcome was global improvement in IBS. Patients were then asked to keep a weekly symptom diary for 10 weeks.

RESULTS

Over the 10 weeks of follow-up, rifaximin resulted in greater improvement in IBS symptoms (P = 0.020). In addition, rifaximin recipients had a lower bloating score after treatment.

LIMITATIONS

The major limitations of the study were its modest sample size and short duration and that most patients were from 1 center.

CONCLUSIONS

Rifaximin improves IBS symptoms for up to 10 weeks after the discontinuation of therapy.