Hydrogen Breath Test an Instrument to Predict Rifaximin-Response in Irritable Bowel Syndrome Predominant Diarrhea

The study aims to determine whether hydrogen breath testing can be used to identify patients
with IBS-D who are more likely to respond to rifaximin. Participating patients will complete
a one week screening period when brief daily survey will be answered. Eligible patients will
proceed with the treatment phase of the study, when patients will receive a 14 day course of
rifaximin. All included patients will complete glucose and lactulose hydrogen breath tests
before and after rifaximin treatment. Biological samples (e.g. blood, stool) will be
collected at pre-determined time points and patients will answer daily brief survey for the
duration of the study.

It is anticipated that 210 patients will be screened to reach a goal of enrolling 110
patients for the treatment phase of the study.

Inclusion Criteria:

- IBS-D (Rome IV Diagnostic Criteria)

- Diary compliance for at least 5 days and no rescue medications during baseline

- Appropriate levels of abdominal pain and diarrhea

Exclusion Criteria:

- Pregnant women or planning on becoming pregnant while in the study, or lactating women
while in the study

- Inflammatory bowel disease, diabetes mellitus, systemic sclerosis, or celiac disease

- Active gastrointestinal or hematological malignancy which requires ongoing treatment

- Surgery to the GI tract in the past 3 months

- Gastrointestinal infection or diverticulitis in the past 3 months

- Severe hepatic impairment

- Any use of antibiotics in the past month

- Current use of probiotics

- Any history of allergies to rifaximin or its derivatives

- Any comitant use of P-glycoprotein inhibitors (for example. Cyclosporine)

- Known allergies to glucose or lactulose