BackgroundRifaximin is a minimally absorbed antibiotic with high luminal activity, used to treat various gastrointestinal diseases. Although rifaximin has been proposed as first line treatment for small intestinal bacterial overgrowth (SIBO), few data are available regarding its efficacy in non-IBS subjects. We aimed to assess the ability of rifaximin to normalize lactulose-H2 breath tests in non-IBS subjects with symptoms suggestive of SIBO.Materials and methodsConsecutive non-IBS patients presenting with bloating and flatulence were prospectively recruited and submitted to lactulose-H2 breath testing (LBT). Patients who had a positive result were offered rifaximin 1200 mg daily for 10 days. Breath testing was repeated two weeks after treatment completion in all patients in order to assess for response.ResultsA total of 19 patients with a positive result received rifaximin and repeated the breath test (7 (36.8%) males, age 56.5 ± 17.6 years). The mean peak hydrogen excretion was 13.7 ± 2.8 and 10.3 ± 7.3 ppm at baseline and following rifaximin treatment, respectively (t = 1.98, p = 0.06). LBT normalized in 8/19 (42.1%) subjects. No patients reported symptom resolution. No adverse events were reported.DiscussionStrengths include the study's prospective design. Limitations include the small sample size and open label design.ConclusionRifaximin was not effective in normalizing LBT in our cohort of non-IBS subjects with symptoms suggestive of SIBO.

The LBT may serve as a diagnostic screening tool for lactose malabsorption. Symptomatic patients with negative LBT results should be referred for second-line testing with the LIQT.

Short-term storage of 1 month does not affect sample stability or the results of (13) C-urea breath tests in up to three consecutive repeats.

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