title: Effects of Rifaximin on Transit, Permeability, Fecal Microbiome, and Organic Acid Excretion in Irritable Bowel Syndrome.
abstract: OBJECTIVE
  Rifaximin relieves irritable bowel syndrome (IBS) symptoms, bloating, abdominal pain, and loose or watery stools. Our objective was to investigate digestive functions in rifaximin-treated IBS patients.
  
  
  METHODS
  In a randomized, double-blind, placebo-controlled, parallel-group study, we compared the effects of rifaximin, 550 mg t.i.d., and placebo for 14 days in nonconstipated IBS and no evidence of small intestinal bacterial overgrowth (SIBO). All subjects completed baseline and on-treatment evaluation of colonic transit by scintigraphy, mucosal permeability by lactulose-mannitol excretion, and fecal microbiome, bile acids, and short chain fatty acids measured on random stool sample. Overall comparison of primary response measures between treatment groups was assessed using intention-to-treat analysis of covariance (ANCOVA, with baseline value as covariate).
  
  
  RESULTS
  There were no significant effects of treatment on bowel symptoms, small bowel or colonic permeability, or colonic transit at 24 h. Rifaximin was associated with acceleration of ascending colon emptying (14.9±2.6 h placebo; 6.9±0.9 h rifaximin; P=0.033) and overall colonic transit at 48 h (geometric center 4.0±0.3 h placebo; 4.7±0.2 h rifaximin; P=0.046); however, rifaximin did not significantly alter total fecal bile acids per g of stool or proportion of individual bile acids or acetate, propionate, or butyrate in stool. Microbiome studies showed strong associations within subjects, modest associations with time across subjects, and a small but significant association of microbial richness with treatment arm (rifaximin vs. treatment).
  
  
  CONCLUSIONS
  In nonconstipated IBS without documented SIBO, rifaximin treatment is associated with acceleration of colonic transit and changes in microbial richness; the mechanism for reported symptomatic benefit requires further investigation.
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Andrés
authors.initials: A
authors.lastname: Acosta
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Camilleri
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Shin
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Linker Nord
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: O'Neill
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Amber V
authors.initials: AV
authors.lastname: Gray
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Lueke
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Donato
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Duane D
authors.initials: DD
authors.lastname: Burton
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Lawrence A
authors.initials: LA
authors.lastname: Szarka
authors.affiliation: Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER), Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Zinsmeister
authors.affiliation: Salix Pharmaceuticals, Raleigh, North Carolina, USA.
authors.forename: Pamela L
authors.initials: PL
authors.lastname: Golden
authors.affiliation: Bioinformatics/Computer Science, University of North Carolina-Charlotte, Charlotte, North Carolina, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Fodor