Antibiotic treatment of constipation-predominant irritable bowel syndrome.
BACKGROUND
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.


OBJECTIVE
To determine the effectiveness of neomycin alone or with rifaximin in improving symptoms in methane-positive C-IBS subjects.


METHODS
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.


RESULTS
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).


CONCLUSIONS
Rifaximin plus neomycin is superior to neomycin alone in improving multiple C-IBS symptoms. This effect is predicted by a reduction in breath methane.
GI Motility Program, Cedars-Sinai Medical Center, Los Angeles, CA, 90048, USA, pimentelm@cshs.org.
Mark
M
Pimentel
Christopher
C
Chang
Kathleen Shari
KS
Chua
James
J
Mirocha
John
J
DiBaise
Satish
S
Rao
Meridythe
M
Amichai
D000328:Adult; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001944:Breath Tests; D003248:Constipation / Q000473:pathology*; D005260:Female; D005765:Gastrointestinal Agents / Q000008:administration & dosage / Q000627:therapeutic use; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000188:drug therapy* / Q000473:pathology*; D008297:Male; D008697:Methane; D008875:Middle Aged; D009355:Neomycin / Q000008:administration & dosage / Q000627:therapeutic use; D012294:Rifamycins / Q000008:administration & dosage / Q000627:therapeutic use*; D000078262:Rifaximin
D000890:Anti-Infective Agents; D005765:Gastrointestinal Agents; D012294:Rifamycins; D009355:Neomycin; D000078262:Rifaximin; D008697:Methane