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J Clin Gastroenterol. 2010 Sep;44(8):547-50. doi: 10.1097/MCG.0b013e3181c64c90.

A combination of rifaximin and neomycin is most effective in treating irritable bowel syndrome patients with methane on lactulose breath test.

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GI Motility Program, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.



There is a growing interest in methane and its association with constipation in functional bowel disease. Neomycin-based treatment of methane-positive subjects has resulted in improvement of constipation. Rifaximin, although superior for the treatment of irritable bowel syndrome compared with other antibiotics, seems less effective in methane-positive subjects. In this study, we evaluate 3 different antibiotic treatments in patients who have a methane-positive breath test: rifaximin only, neomycin only, and the combination of neomycin and rifaximin.


A retrospective chart review was conducted on patients with methane on their lactulose breath test (> or =3 ppm of methane) who received one of the following antibiotic treatments: 500 mg b.i.d. for 10 days of neomycin alone, 400 mg t.i.d. for 10 days of rifaximin alone, or a combination of both rifaximin and neomycin for 10 days. All patients must have received antibiotic treatment after their initial consultation at the medical center and, in addition, had at least 1 follow-up to evaluate the effects of the treatment. After inclusion/exclusion criteria were met, all charts were evaluated to determine if the subject was a responder to the antibiotic therapy. This included clinical symptom improvement and eradication of methane on their breath test.


Of the subjects receiving the treatment of rifaximin and neomycin (n=27), 85% had a clinical response, compared with 63% of subjects in the neomycin only group (n=8) (P=0.15) and 56% of subjects in the rifaximin only group (n=39) (P=0.01). When comparing the neomycin group with the rifaximin group, the difference was nonsignificant. When evaluating methane eradication results, 87% of subjects taking the rifaximin and neomycin combination eradicated the methane on their breath test. This is compared with 33% of subjects in the neomycin group that eradicated the methane (P=0.001), and only 28% of subjects in the rifaximin group (P=0.001). Of the patients who did not eliminate the methane with only rifaximin treatment, 66% of those who subsequently used the rifaximin and neomycin treatment were able to normalize their breath test.


The combination of rifaximin and neomycin is more effective in treating methane-producing subjects-in both clinical response and methane elimination.

[Indexed for MEDLINE]

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