Phase 4 N=74 Randomized Treatment

A Longitudinal Study to Identify IBS Phenotypes Using Fecal Microbiota and Hydrogen Breath Testing

Irritable Bowel Syndrome

Bottom Line

View on ClinicalTrials.gov: NCT03219528 ↗

Enrolled (actual)

Serious AEs

0.0%

Results posted

Apr 2025

Primary outcome: Primary: Change in Mean Daily Abdominal Pain — 5.2; 5.3; 3.9; 3.8 score on a scale — p=0.78

Study Design & Population

Study type: Interventional
Phase: Phase 4
Interventions: Rifaximin 550 MG (Drug); Low FODMAP Diet (Other)
Age: Adult, Older Adult · 18+ yrs
Sex: All
Sponsor: University of Michigan
Primary completion: Feb 2024

Outcome Measures

Outcome	Result	p-value
PRIMARY Change in Mean Daily Abdominal Pain	5.2; 5.3; 3.9; 3.8	0.78
PRIMARY Change in Mean Daily Bloating	4.9; 5.1; 4.0; 3.7	0.77
SECONDARY Change in Irritable Bowel Syndrome (IBS) Symptom Severity Scale	281.3; 272.0; 209.3; 194.7	—
SECONDARY Change in Gastrointestinal System Ratings Scale (GSRS)	52.0; 52.1; 40.7; 40.1	—
SECONDARY Change in Stool Form	5.6; 5.6; 5.0; 5.3	—
SECONDARY Change in Psychological Function	8.6; 8.3; 6.2; 5.8	—
SECONDARY Change in Irritable Bowel Syndrome Quality of Life Instrument (IBS-QOL)	53.6; 58.9; 62.6; 67.8	—
SECONDARY 24-hour Diet Recall/Intake - Lactose	4.1; 7.3; 5.1; 1.4	—
SECONDARY 24-hour Diet Recall/Intake - Gluten	6.7; 5.7; 7.2; 1.7	—

Summary

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a highly prevalent but poorly understood condition with limited treatment options. Current therapies, including a nonabsorbable antibiotic rifaximin or diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP), show efficacy in 50% or less of patients. In this proposal, participants with IBS-D will be randomized to receive either rifaximin or low FODMAP dietary intervention.

Eligibility Criteria

Inclusion Criteria

Adult subjects greater than or equal to 18 years of age who meet Rome IV criteria for diarrhea-predominant irritable bowel syndrome (IBS-D).

Prior colonoscopy or sigmoidoscopy within the past 2 years with random colon biopsies to exclude the presence of microscopic colitis.

IBS medications, including anti-depressants, will be allowed if the dose has been stable for at least 1 month before inclusion. Medications will be carefully tracked to follow any potential confounding issues.

Exclusion Criteria

Underlying celiac disease, inflammatory bowel disease, or other organic disease that could explain their symptoms.

Subjects with a history of GI tract surgery, except for cholecystectomy or appendectomy, will also be excluded from the study.

Women who are pregnant or breastfeeding Antibiotics taken within 3 months prior to enrollment will not be permitted. Subjects on probiotics must discontinue their use at least 1 month prior to enrollment.

Subjects who have previously received formal dietary education for IBS, including a low FODMAP diet, or previously received antibiotics, including rifaximin, for treatment of IBS-D will be excluded from the study.

View full record on ClinicalTrials.gov →

Data sourced from ClinicalTrials.gov (NCT03219528). Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication.