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A Combination of Rifaximin and Neomycin Is Most Effective in Treating Irritable Bowel Syndrome Patients With Methane on Lactulose Breath Test

Low, Kimberly BA; Hwang, Laura BS; Hua, Johnson MD; Zhu, Amy MD; Morales, Walter BS; Pimentel, Mark MD

Journal of Clinical Gastroenterology: September 2010 - Volume 44 - Issue 8 - p 547-550
doi: 10.1097/MCG.0b013e3181c64c90
Original Article

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.

Methods A retrospective chart review was conducted on patients with methane on their lactulose breath test (≥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.

Results 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.

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

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

Source of Support: Financial support for this study was provided by Salix Pharmaceuticals. Further support was provided by the Beatrice and Samuel A. Seaver Foundation.

Reprints: Mark Pimentel, MD, FRCP(C), Director, GI Motility Program, Cedars-Sinai Medical Center, 8730 Alden Drive, Suite 225E, Los Angeles, CA 90048 (e-mail:

Received for publication July 21, 2009

accepted October 13, 2009

Conflict of Interest Statement: Mark Pimentel has other grant support including Prometheus Pharmaceuticals. He is a consultant for Prometheus Pharmaceuticals and Salix Pharmaceuticals. In addition, Cedars-Sinai Medical Center has a licensing agreement with both Prometheus and Salix Pharmaceuticals.

© 2010 Lippincott Williams & Wilkins, Inc.