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.
Dr Mark Pimentel and colleagues determined the effectiveness of neomycin alone or with rifaximin in improving symptoms in methane-positive C-IBS subjects.
The research team performed a double-blind, randomized, placebo-controlled trial from 2010 to 2013 at 3 tertiary care centers.
Subjects aged 18–65 with C-IBS and breath methane meeting the inclusion and exclusion criteria were recruited.
|Constipation severity was significantly lower in the neomycin and rifaximin group|
|Digestive Diseases & Sciences|
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.
The researchers assessed symptom severity by weekly questionnaire for 2 weeks of therapy and 4 additional weeks of follow-up.
The team included 31 subjects in the intention-to-treat analysis.
The research team noted that constipation severity was significantly lower in the neomycin and rifaximin group compared to neomycin alone, with greater improvement in constipation, straining and bloating, but not abdominal pain.
In the neomycin and rifaximin group, subjects with methane <3 ppm after treatment reported significantly lower constipation severity than subjects with persistent methane.
Dr Pimentel's team concludes, "Rifaximin plus neomycin is superior to neomycin alone in improving multiple C-IBS symptoms."
"This effect is predicted by a reduction in breath methane."