Antibiotic Treatment of Constipation-Predominant Irritable Bowel Syndrome
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The antibiotic rifaximin is used to treat non-constipated irritable bowel syndrome (IBS). Methane production is associated with constipation and its severity in constipation-predominant IBS (C-IBS). A previous retrospective study suggested that rifaximin and neomycin was superior to neomycin alone in improving symptoms in methane-positive subjects.
To determine the effectiveness of neomycin alone or with rifaximin in improving symptoms in methane-positive C-IBS subjects.
A double-blind, randomized, placebo-controlled trial was performed from 2010 to 2013 at three tertiary care centers. Subjects aged 18–65 with C-IBS (Rome II criteria) and breath methane (>3 ppm) meeting the inclusion and exclusion criteria were recruited. Subjects completed a baseline symptom questionnaire rating the severity of abdominal and bowel symptoms on a visual analog scale and were randomized to receive neomycin and placebo or neomycin and rifaximin for 14 days. Symptom severity was assessed by weekly questionnaire for 2 weeks of therapy and 4 additional weeks of follow-up.
Thirty-one subjects (16 neomycin and placebo, 15 neomycin and rifaximin) were included in the intention-to-treat analysis. Constipation severity was significantly lower in the neomycin and rifaximin group (28.6 ± 30.8) compared to neomycin alone (61.2 ± 24.1) (P = 0.0042), with greater improvement in constipation (P = 0.007), straining (P = 0.017) and bloating (P = 0.020), but not abdominal pain. In the neomycin and rifaximin group, subjects with methane <3 ppm after treatment reported significantly lower constipation severity (30.5 ± 21.8) than subjects with persistent methane (67.2 ± 32.1) (P = 0.020).
Rifaximin plus neomycin is superior to neomycin alone in improving multiple C-IBS symptoms. This effect is predicted by a reduction in breath methane.
KeywordsIrritable bowel syndrome Constipation Antibiotics Breath methane
This study was supported by funding from Salix Pharmaceuticals. Salix provided the placebo and rifaximin for this study and was responsible for the randomization of study subjects and blinding of investigators to the study drugs during the conduct of the study, but were not involved in any other aspect of the study including implementation, recruitment, analysis or construction of the manuscript.
Conflict of interest
Dr. Pimentel has received grants from and is a consultant for Salix Pharmaceuticals, with whom Cedars-Sinai has a licensing agreement. The remaining authors have nothing to disclose. This study was supported by funding from Salix Pharmaceuticals.
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