Combining a low-FODMAP diet with mirtazapine to treat IBS with diarrhea

Novel Pilot Study to Treat Symptoms of IBS With Diarrhea Using Combination Therapy of a Low-FODMAP Diet and a Neuromodulator

Early Phase 1 Interventional Mayo Clinic · NCT06684470

This study is testing if combining a low-FODMAP diet with the medication mirtazapine can help adults with diarrhea-predominant irritable bowel syndrome feel better and improve their quality of life.

Quick facts

PhaseEarly Phase 1
Study typeInterventional
Enrollment20 (estimated)
Ages18 Years to 70 Years
SexAll
SponsorMayo Clinic Academic / other
Locations1 site (Jacksonville, Florida)
Trial IDNCT06684470 on ClinicalTrials.gov

What this trial studies

This research investigates the effectiveness of a combination therapy involving a low-FODMAP diet and the medication mirtazapine for treating symptoms of diarrhea-predominant irritable bowel syndrome (IBS-D). Participants will be adults aged 18-70 who meet specific criteria for IBS-D and will be evaluated for improvements in symptoms such as abdominal pain and diarrhea using validated questionnaires. The study aims to determine if the combination therapy leads to greater symptom relief and improved quality of life compared to the diet alone.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18-70 with a diagnosis of diarrhea-predominant IBS and a score greater than 175 on the IBS-SSS questionnaire.

Not a fit: Patients with prior diagnoses of celiac disease, inflammatory bowel disease, or those with ongoing significant anxiety or depression may not benefit from this study.

Why it matters

Potential benefit: If successful, this approach could provide a new effective treatment option for patients suffering from IBS-D.

How similar studies have performed: While the combination of a low-FODMAP diet and mirtazapine is a novel approach, similar dietary interventions have shown promise in managing IBS symptoms in other studies.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Participants must meet all of the inclusion criteria to participate in this study:

  * Adults (ages 18-70)
  * Score of \>175 on the IBS-SSS questionnaire
  * Must meet Rome IV criteria for IBS-D
  * If subject is of reproductive capability a negative urine pregnancy test must be available prior to entering the study
  * Ability to understand study procedures and to comply with them for the entire length of the study

Exclusion Criteria:

* All candidates meeting any of the below exclusion criteria at baseline will be excluded from study participation:

  * Score of \< 175 on the IBS-SSS
  * Prior diagnoses of: known celiac disease, small intestinal bacterial overgrowth, inflammatory bowel disease, or microscopic colitis
  * Ongoing significant anxiety or depression
  * A history of a known side effect to mirtazapine
  * Prior treatment with a low FODMAP diet or mirtazapine without clinical benefit
  * Active alcohol or drug abuse
  * Inability to read or understand the consent form
  * Any other medical or psychological reason that would prevent active participation in a research study
  * Pregnant females

Where this trial is running

Jacksonville, Florida

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions IBS - Irritable Bowel SyndromeDiarrheaIBSIrritable Bowel Syndrome
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.