Clinical Question: Does rifaximin (Xifaxan) reduce abdominal bloating and flatulence?

Setting: Outpatient (any)

Study Design: Randomized controlled trial (double-blinded)

Allocation: Concealed

Synopsis: It is thought that bloating and flatulence, especially troublesome in patients with irritable bowel syndrome (IBS), may be caused by bacterial overgrowth in the small intestine. The theory is that this overgrowth can be detected by measuring hydrogen released during bacterial carbohydrate fermentation with a lactulose hydrogen breath test (LHBT). Previous studies with neomycin to kill these bacteria have provided promising results, but symptoms recurred quickly after the antibiotic was discontinued.

In this study, the researchers recruited 126 adults with at least 12 weeks of bloating or excessive flatulence and at least one other lower abdominal symptom. The mean age of participants was 40 years, 57 percent met Rome II criteria for IBS, and 55 percent were women. After a 10-day baseline evaluation period, patients were randomized (allocation concealed) to receive 400 mg rifaximin twice daily or placebo for 10 days.

Outcomes were assessed at the end of the 10-day evaluation period and again 10 days later. The primary end point was the patient response to the question, “Do you consider that your symptoms have improved since starting the study drug?” A favorable response was reported more often at the end of the 10-day study period (41 versus 23 percent; P = .03; number needed to treat [NNT] = 6), as well as after the final 10-day period during which no medications were given (28.6 versus 11.5 percent; P = .02; NNT = 6). The benefit was similar for the subgroup of patients with IBS.

The authors did some data dredging and found that changes in LHBT results correlated with bloating scores in those who responded to rifaximin but not in those who did not. This post-hoc analysis may point toward future research but cannot guide therapy. The drug was well tolerated (it is not absorbed by the gastrointestinal tract); the authors claimed no adverse effects related to treatment in either group. The cost of the drug is high ($100 for 400 mg twice daily for seven days)

Bottom Line: A 10-day course of rifaximin reduced bloating and flatulence in patients with and without IBS. Although larger, longer-term studies are needed before this approach is widely adopted for all patients with IBS, it could be considered now for patients with especially troublesome symptoms. (Level of Evidence: 1b)