BloatingPhase 3NCT07522255
Rifaximin Treatment in Bloating Predominant Functional Bowel Disorders
A Phase 3 study testing Rifaximin (drug) in people with Bloating and Rifaximin, run by Mahidol University at 1 site in Thailand.
Trial summary
This randomized, double-blind, placebo-controlled trial will evaluate the effects of a 14-day course of rifaximin on bloating symptoms, gut microbiota, microbial metabolites, and intestinal gases in adults with Rome V irritable bowel syndrome with constipation (IBS-C) or functional abdominal bloating (FAB). Read more about this study
- Who is it for?
- Ages 18 to 80 years
- Conditions the study is for
- Bloating, Rifaximin, Functional Bowel Disorder
- What is being tested?
- Rifaximin (drug)
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 78 participants
- Where
- 1 siteThailand
- Study dates
- Dec 2026to Dec 2028
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 80 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Adults aged 18 to 80 years.
- Rome V diagnosis of irritable bowel syndrome with constipation, or functional abdominal bloating.
- Bothersome bloating with baseline severity of at least 3 on a 7-point Likert scale after adequate constipation treatment, defined as stool frequency from at least 3 times/week to 3 times/day and Bristol Stool Form Scale type 3-5.
- Colonoscopy, CT colonography, or barium enema performed if clinically indicated as part of standard evaluation for bowel symptoms.
Who cannot join
- History of major gastrointestinal surgery, except appendectomy or laparoscopic cholecystectomy.
- Inflammatory bowel disease or other inflammatory gastrointestinal conditions.
- Current use of, or inability to discontinue, medications that may affect intestinal microbiota or gas measurements, including antibiotics, proton pump inhibitors, probiotics, lactulose, NSAIDs, or metformin.
- Current use of, or inability to discontinue, medications that may affect bloating symptoms, including simethicone, simethicone-containing antispasmodics, or antidiarrheal medications.
- Underlying conditions known to affect intestinal microbiota composition, including cirrhosis, uncontrolled diabetes mellitus, end-stage renal disease, obesity, malignancy, or psychiatric disorders.
- Opioid-induced constipation.
- Known allergy to rifaximin.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
Thailand1 site
Faculty of Medicine Siriraj Hospital, Mahidol University
Bangkok Noi, Bangkok, 10700
About this study
Official title: Effects of Rifaximin on Bloating, Gut Microbiome, Metabolome, and Intestinal Gas in Patients With Irritable Bowel Syndrome With Constipation or Functional Abdominal Bloating Defined by Rome V Criteria: A Randomized, Double-Blind, Placebo-Controlled Trial
This randomized, double-blind, placebo-controlled trial will evaluate the effects of a 14-day course of rifaximin on bloating symptoms, gut microbiota, microbial metabolites, and intestinal gases in adults with Rome V irritable bowel syndrome with constipation (IBS-C) or functional abdominal bloating (FAB). Participants with predominant, bothersome bloating despite adequate bowel movement management will be randomly assigned in a 1:1 ratio to receive rifaximin 550 mg three times daily or matching placebo for 2 weeks. The primary endpoint is the proportion of participants with a bloating response, defined as at least a 1-point reduction from baseline on a 7-point Likert bloating scale at the end of treatment. Additional assessments will include other gastrointestinal symptoms, quality of life, psychological symptoms, gut microbiota diversity and composition, fecal short-chain fatty acids, plasma bile acids and gut-derived uremic toxins, and breath hydrogen and methane levels. Associations between biological changes and clinical response will also be examined.
Read the detailed description
Abdominal bloating is a common and bothersome symptom in disorders of gut-brain interaction, including irritable bowel syndrome with constipation (IBS-C) and functional abdominal bloating (FAB). Its mechanisms may include altered gastrointestinal motility, visceral hypersensitivity, microbial fermentation, and changes in intestinal microbiota. Symptoms may persist despite adequate management of constipation, and treatment options specifically targeting bloating remain limited.
Rifaximin is a minimally absorbed oral antibiotic that may improve bloating by modifying intestinal microbiota and microbial metabolic activity. This randomized, double-blind, placebo-controlled, parallel-group trial will evaluate its effects on bloating and associated biological measures in adults aged 18-80 years with Rome V IBS-C or FAB. Eligible participants must have predominant, bothersome bloating, with a score of at least 3 on a 7-point Likert scale, despite adequate bowel movement management.
Participants will be randomly assigned in a 1:1 ratio to receive rifaximin 550 mg three times daily or matching placebo for 14 days. Computer-generated randomization will use blocks of four, with stratification by diagnostic subgroup. Participants, treating physicians, and investigators will remain blinded to treatment allocation.
Baseline assessments will include demographic and clinical characteristics, gastrointestinal symptoms, bowel habits, quality of life, and depression, anxiety, and stress symptoms. Stool samples will be collected for gut microbiota profiling using shotgun metagenomics and measurement of fecal short-chain fatty acids. Blood samples will be collected to measure plasma bile acids and gut-derived uremic toxins. Lactulose breath testing will assess hydrogen and methane levels. Clinical and laboratory assessments will be repeated at the end of treatment.
During treatment, participants will record daily bloating and abdominal pain scores, bowel movement frequency, stool consistency using the Bristol Stool Form Scale, and rescue medication use. Prespecified rescue medications will be permitted for breakthrough symptoms. A telephone assessment at week 1 will evaluate symptoms, quality of life, psychological symptoms, treatment satisfaction, medication adherence, and adverse events.
The primary endpoint is the proportion of participants with a bloating response, defined as at least a 1-point reduction from baseline on the 7-point Likert bloating scale at the end of treatment. Secondary outcomes include abdominal pain, IBS symptom severity, bowel habits, quality of life, depression, anxiety and stress scores, treatment satisfaction, and rescue medication use. Biological outcomes include changes in gut microbiota diversity and composition, fecal short-chain fatty acids, plasma bile acids and gut-derived uremic toxins, and breath hydrogen and methane levels. Analyses will also examine associations between biological measures and clinical outcomes and identify baseline factors associated with treatment response.
- Conditions
- Bloating, Rifaximin, Functional Bowel Disorder, Irritable Bowel Syndrome, Constipation, Microbiota
- Being tested
- Rifaximin (drug), Placebo
- Keywords
- Rifaximin, Bloating, Functional bowel disorder, Gut microbiota, Metabolome
- Medical subject headings
- Irritable Bowel Syndrome, Constipation
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Rifaximin (drug)Drug
Participants randomized to this arm receive rifaximin 550 mg orally three times daily for 2 weeks. Allocation is randomized and double-blinded.
PlaceboDrug
Matching placebo administered orally three times daily for 14 days.
| Study group | Role | What they receive |
|---|---|---|
| Rifaximin | Experimental | Participants randomized to this arm receive rifaximin 550 mg orally three times daily for 2 weeks. Receives: Drug: Rifaximin (drug) |
| Placebo | Placebo comparator | Participants randomized to this arm receive an identical placebo orally three times daily for 2 weeks. Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Bloating responder rate
Bloating responder is defined as at least a 1-point reduction from baseline to week 2 in bloating symptom severity measured using a 7-point Likert scale for bothersomeness of bloating (range 0 to 6; higher scores indicate worse symptoms). Score categories are 0 = not at all, 1 = hardly, 2 = somewhat, 3 = moderately, 4 = a good deal, 5 = a great deal, and 6 = a very great deal.
Measured: From enrollment to the end of treatment at 2 weeks
Secondary outcomes (21)
Abdominal pain response rate
Abdominal pain responder is defined as at least a 1-point reduction from baseline to week 2 in abdominal pain severity measured using a 7-point Likert scale for bothersomeness of abdominal pain (range 0 to 6; higher scores indicate worse symptoms). Score categories are 0 = not at all, 1 = hardly, 2 = somewhat, 3 = moderately, 4 = a good deal, 5 = a great deal, and 6 = a very great deal.
Measured: From enrollment to the end of treatment at 2 weeks
Change in Global IBS Symptoms (IBS-C patients)
Change in IBS Symptom Severity Score (IBS-SSS) from baseline, assessing overall IBS symptom burden, abdominal pain, bloating, and bowel habit changes. The IBS-SSS scale ranges from 0 to 500, with higher scores indicating more severe IBS symptoms.
Measured: From enrollment to the end of treatment at 2 weeks
Treatment satisfaction
Overall treatment satisfaction, measured using a Visual Analog Scale (VAS) ranging from 0 to 10:
0 = Completely Dissatisfied 10 = Completely Satisfied Higher scores indicate greater satisfaction with treatment. The difference between baseline and post-intervention scores will be analyzed.
Measured: End of treatment at 2 weeks
Change in Psychological Symptoms
Change in Depression, Anxiety, and Stress Scores (DASS-21), a validated self-reported scale measuring psychological distress. The DASS-21 consists of three subscales:
Depression (0-21) Anxiety (0-21) Stress (0-21) Each subscale score ranges from 0 (normal) to 21 (severe symptoms), with higher scores indicating greater psychological distress. The total score is calculated by summing individual subscale scores.
Measured: From enrollment to the end of treatment at 2 weeks
Change in Quality of Life (IBS-C patients)
Change in IBS-specific Quality of Life (IBS-QoL) score, which assesses the impact of IBS on daily activities, emotional well-being, and social functioning.
The IBS-QoL score ranges from 0 to 100, with higher scores indicating better quality of life.
Measured: From enrollment to the end of treatment at 2 weeks
Change in quality of life (FAB patients)
The quality of life of patients with FAB/D was measure with 36-Item Short Form Health Survey (SF-36). The SF-36 assesses health-related quality of life across 8 domains: physical functioning, role limitations due to physical health, role limitations due to emotional problems, energy/fatigue, emotional well-being, social functioning, pain, and general health. Each domain score is transformed to a 0 to 100 scale, with higher scores indicating better health status.
Measured: From enrollment to the end of treatment at 2 weeks
Stool microbiota diversity and composition
Change from baseline in stool microbiota alpha diversity, beta diversity, and taxonomic abundance measured by shotgun metagenomics.
Measured: From enrollment to the end of treatment at 2 weeks
Change in intestinal gas measurement (hydrogen)
Change from baseline in hydrogen gas production measured in part per million unit during lactulose hydrogen breath testing.
Measured: From enrollment to the end of treatment at 2 weeks
Change in intestinal gas measurement (methane)
Change from baseline in methane gas production measured in part per million unit during lactulose hydrogen breath testing.
Measured: From enrollment to the end of treatment at 2 weeks
Proportion of patients with positive lactulose hydrogen breath test
A positive lactulose hydrogen breath test is defined as either a rise in breath hydrogen of 20 ppm or more above baseline within 90 minutes or a breath methane concentration of 10 ppm or more at any time during the test after ingestion of 10 g lactulose. Breath samples are collected every 15 to 30 minutes for up to 180 minutes. Higher proportions indicate a worse outcome (more abnormal breath test results).
Measured: From enrollment to the end of treatment at 2 weeks
Rescue medication use
Frequency and dose of rescue medications used for breakthrough symptoms during the treatment period.
Measured: From enrollment to the end of treatment at 2 weeks
Adverse events
Incidence of treatment-emergent adverse events.
Measured: From enrollment to the end of treatment at 2 weeks
Association between baseline bloating symptom severity score and bloating response at 2 weeks
Exploratory analysis of whether baseline bloating symptom severity predicts treatment response. Baseline bloating symptom severity is assessed using a 7-point Likert scale for bothersomeness of bloating (score range 0 to 6; higher scores indicate worse symptoms). The association between baseline score and bloating responder status at 2 weeks will be evaluated using logistic regression and reported as an odds ratio. Bloating responder is defined as at least a 1-point reduction from baseline in bloating symptom severity score.
Measured: Baseline predictor with treatment response assessed at 2 weeks
Association between baseline fecal microbiota alpha diversity and bloating response at 2 weeks
Exploratory analysis of whether baseline fecal microbiota alpha diversity predicts treatment response. Baseline stool microbiota is assessed using 16S rRNA sequencing. Alpha diversity will be assessed using the Shannon diversity index. The association between baseline Shannon diversity index and bloating responder status at 2 weeks will be evaluated using logistic regression and reported as an odds ratio. Bloating responder is defined as at least a 1-point reduction from baseline in bloating symptom severity score.
Measured: Baseline predictor with treatment response assessed at 2 weeks
Association between baseline positive diagnosis of small intestinal bacterial overgrowth and bloating response at 2 weeks
Exploratory analysis of whether baseline small intestinal bacterial overgrowth (SIBO) status predicts treatment response. Baseline SIBO status will be assessed using a lactulose hydrogen-methane breath test after ingestion of 10 g lactulose, with breath samples collected every 15 to 30 minutes for up to 180 minutes. A positive SIBO diagnosis is defined as a rise in breath hydrogen of 20 parts per million or more above baseline within 90 minutes. The association between baseline positive SIBO status (yes/no) and bloating responder status at 2 weeks will be evaluated using logistic regression and reported as an odds ratio. Bloating responder is defined as at least a 1-point reduction from baseline in bloating symptom severity score.
Measured: Baseline predictor with treatment response assessed at 2 weeks.
Association between baseline positive diagnosis of intestinal methanogen overgrowth and bloating response at 2 weeks
Exploratory analysis of whether baseline intestinal methanogen overgrowth (IMO) status predicts treatment response. Baseline IMO status will be assessed using a lactulose hydrogen-methane breath test after ingestion of 10 g lactulose, with breath samples collected every 15 to 30 minutes for up to 180 minutes. A positive IMO diagnosis is defined as a breath methane concentration of 10 parts per million or more at any time during the test. The association between baseline positive IMO status (yes/no) and bloating responder status at 2 weeks will be evaluated using logistic regression and reported as an odds ratio. Bloating responder is defined as at least a 1-point reduction from baseline in bloating symptom severity score.
Measured: Baseline predictor with treatment response assessed at 2 weeks.
Changes in fecal short-chain fatty acid concentrations
Between-group differences in changes from baseline in fecal short-chain fatty acid concentrations following rifaximin or placebo treatment.
Measured: From enrollment to the end of treatment at 2 weeks
Changes in plasma bile acid concentrations
Between-group differences in changes from baseline in plasma bile acid concentrations following rifaximin or placebo treatment.
Measured: From enrollment to the end of treatment at 2 weeks
Changes in gut-derived uremic toxin concentrations
Between-group differences in changes from baseline in plasma gut-derived uremic toxin concentrations following rifaximin or placebo treatment.
Measured: From enrollment to the end of treatment at 2 weeks
Bloating response at weeks 4
Proportion of participants in each treatment group with at least a 1-point reduction from baseline on the 7-point Likert bloating scale, assessed by telephone at weeks 4.
Measured: From enrollment to 4 weeks
Bloating response at weeks 8
Proportion of participants in each treatment group with at least a 1-point reduction from baseline on the 7-point Likert bloating scale, assessed by telephone at weeks 8.
Measured: From enrollment to 8 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted13 Apr 2026
- Study startDec 2026 (estimated)
- Primary completionJun 2028 (estimated)
- Study completionDec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (6)Papers the sponsor has linked to this study.
- Other trials for BloatingStudies of the same condition, open and under way.
- More trials run by Mahidol UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 78 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Mahidol University
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Monthira Maneerattanaporn, M.D., Principal investigator, Mahidol UniversityPubet Weeranawin, M.D., Study chair, Mahidol UniversitySomchai Leelakusolvong, M.D., Study chair, Mahidol UniversityTanawat Geeratragool, M.D., Study chair, Mahidol University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07522255
- Sponsor's protocol ID
- Si 917/2025
- Status last verified
- Oct 2026
- First submitted
- 23 Mar 2026
- Last updated
- 27 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: To protect participant confidentiality and comply with institutional and regulatory requirements, no IPD will be shared unless with reasonable request.
Publications
Mearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M, Spiller R. Bowel Disorders. Gastroenterology. 2016 Feb 18:S0016-5085(16)00222-5. doi: 10.1053/j.gastro.2016.02.031. Online ahead of print.
PubMed 27144627Lacy BE, Chang L, Rao SSC, Heimanson Z, Sayuk GS. Rifaximin Treatment for Individual and Multiple Symptoms of Irritable Bowel Syndrome With Diarrhea: An Analysis Using New End Points. Clin Ther. 2023 Mar;45(3):198-209. doi: 10.1016/j.clinthera.2023.01.010. Epub 2023 Mar 14.
PubMed 36922331Chey WD, Shah ED, DuPont HL. Mechanism of action and therapeutic benefit of rifaximin in patients with irritable bowel syndrome: a narrative review. Ther Adv Gastroenterol. 2020 Jan 23;13:1756284819897531. doi: 10.1177/1756284819897531. eCollection 2020.
PubMed 32047534Melchior C, Hammer H, Bor S, Barba E, Horvat IB, Celebi A, Drug V, Dumitrascu D, Kalkan IH, Hauser G, Lionis C, Livovsky D, Mari A, Mulak A, Surdea-Blaga T, Tack J, Vanuytsel T, Savarino EV, Zarate-Lopez N, Hammer J, Dickman R. European Consensus on Functional Bloating and Abdominal Distension-An ESNM/UEG Recommendations for Clinical Management. United European Gastroenterol J. 2025 Nov;13(9):1613-1651. doi: 10.1002/ueg2.70098. Epub 2025 Aug 22.
PubMed 40844856Moshiree B, Drossman D, Shaukat A. AGA Clinical Practice Update on Evaluation and Management of Belching, Abdominal Bloating, and Distention: Expert Review. Gastroenterology. 2023 Sep;165(3):791-800.e3. doi: 10.1053/j.gastro.2023.04.039. Epub 2023 Jul 13.
PubMed 37452811Arora U, Sachdeva K, Garg P, Baitha U, Kedia S, Kalaivani M, Ahuja V, Kumar A, Ranjan P, Vikram NK, Sinha S, Biswas A, Wig N. Efficacy of Rifaximin in Patients With Abdominal Bloating or Distension: A Systematic Review and Meta-analysis. J Clin Gastroenterol. 2024 Apr 1;58(4):360-369. doi: 10.1097/MCG.0000000000001872.
PubMed 37310270
Study at a glance
From the registry record, last updated by the sponsor on 27 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effects of Rifaximin on Bloating, Gut Microbiome, Metabolome, and Intestinal Gas in Patients With Irritable Bowel Syndrome With Constipation or Functional Abdominal Bloating Defined by Rome V Criteria: A Randomized, Double-Blind, Placebo-Controlled Trial
- ClinicalTrials.gov ID
- NCT07522255
- Acronym / sponsor ID
- Si 917/2025
- Conditions
- Bloating, Rifaximin, Functional Bowel Disorder, Irritable Bowel Syndrome, Constipation, Microbiota
- Keywords
- Rifaximin, Bloating, Functional bowel disorder, Gut microbiota, Metabolome
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 78 participants (estimated)
- Lead sponsor
- Mahidol UniversityUniversity, hospital or other
- Study start
- Dec 2026 (estimated)
- Primary completion
- Jun 2028 (estimated)
- Study completion
- Dec 2028 (estimated)
- First posted
- 13 Apr 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This randomized, double-blind, placebo-controlled trial will evaluate the effects of a 14-day course of rifaximin on bloating symptoms, gut microbiota, microbial metabolites, and intestinal gases in adults with Rome V irritable bowel syndrome with constipation (IBS-C) or functional abdominal bloating (FAB). Participants with predominant, bothersome bloating despite adequate bowel movement management will be randomly assigned in a 1:1 ratio to receive rifaximin 550 mg three times daily or matching placebo for 2 weeks. The primary endpoint is the proportion of participants with a bloating response, defined as at least a 1-point reduction from baseline on a 7-point Likert bloating scale at the end of treatment. Additional assessments will include other gastrointestinal symptoms, quality of life, psychological symptoms, gut microbiota diversity and composition, fecal short-chain fatty acids, plasma bile acids and gut-derived uremic toxins, and breath hydrogen and methane levels. Associations between biological changes and clinical response will also be examined.
Detailed description
Abdominal bloating is a common and bothersome symptom in disorders of gut-brain interaction, including irritable bowel syndrome with constipation (IBS-C) and functional abdominal bloating (FAB). Its mechanisms may include altered gastrointestinal motility, visceral hypersensitivity, microbial fermentation, and changes in intestinal microbiota. Symptoms may persist despite adequate management of constipation, and treatment options specifically targeting bloating remain limited.
Rifaximin is a minimally absorbed oral antibiotic that may improve bloating by modifying intestinal microbiota and microbial metabolic activity. This randomized, double-blind, placebo-controlled, parallel-group trial will evaluate its effects on bloating and associated biological measures in adults aged 18-80 years with Rome V IBS-C or FAB. Eligible participants must have predominant, bothersome bloating, with a score of at least 3 on a 7-point Likert scale, despite adequate bowel movement management.
Participants will be randomly assigned in a 1:1 ratio to receive rifaximin 550 mg three times daily or matching placebo for 14 days. Computer-generated randomization will use blocks of four, with stratification by diagnostic subgroup. Participants, treating physicians, and investigators will remain blinded to treatment allocation.
Baseline assessments will include demographic and clinical characteristics, gastrointestinal symptoms, bowel habits, quality of life, and depression, anxiety, and stress symptoms. Stool samples will be collected for gut microbiota profiling using shotgun metagenomics and measurement of fecal short-chain fatty acids. Blood samples will be collected to measure plasma bile acids and gut-derived uremic toxins. Lactulose breath testing will assess hydrogen and methane levels. Clinical and laboratory assessments will be repeated at the end of treatment.
During treatment, participants will record daily bloating and abdominal pain scores, bowel movement frequency, stool consistency using the Bristol Stool Form Scale, and rescue medication use. Prespecified rescue medications will be permitted for breakthrough symptoms. A telephone assessment at week 1 will evaluate symptoms, quality of life, psychological symptoms, treatment satisfaction, medication adherence, and adverse events.
The primary endpoint is the proportion of participants with a bloating response, defined as at least a 1-point reduction from baseline on the 7-point Likert bloating scale at the end of treatment. Secondary outcomes include abdominal pain, IBS symptom severity, bowel habits, quality of life, depression, anxiety and stress scores, treatment satisfaction, and rescue medication use. Biological outcomes include changes in gut microbiota diversity and composition, fecal short-chain fatty acids, plasma bile acids and gut-derived uremic toxins, and breath hydrogen and methane levels. Analyses will also examine associations between biological measures and clinical outcomes and identify baseline factors associated with treatment response.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Rifaximin | Experimental | Drug: Rifaximin (drug)Participants randomized to this arm receive rifaximin 550 mg orally three times daily for 2 weeks. |
| Placebo | Placebo comparator | Drug: PlaceboParticipants randomized to this arm receive an identical placebo orally three times daily for 2 weeks. |
Who may qualify
- Ages
- 18 to 80 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- Adults aged 18 to 80 years.
- Rome V diagnosis of irritable bowel syndrome with constipation, or functional abdominal bloating.
- Bothersome bloating with baseline severity of at least 3 on a 7-point Likert scale after adequate constipation treatment, defined as stool frequency from at least 3 times/week to 3 times/day and Bristol Stool Form Scale type 3-5.
- Colonoscopy, CT colonography, or barium enema performed if clinically indicated as part of standard evaluation for bowel symptoms.
Key exclusion criteria (7 listed)
- History of major gastrointestinal surgery, except appendectomy or laparoscopic cholecystectomy.
- Inflammatory bowel disease or other inflammatory gastrointestinal conditions.
- Current use of, or inability to discontinue, medications that may affect intestinal microbiota or gas measurements, including antibiotics, proton pump inhibitors, probiotics, lactulose, NSAIDs, or metformin.
- Current use of, or inability to discontinue, medications that may affect bloating symptoms, including simethicone, simethicone-containing antispasmodics, or antidiarrheal medications.
- Underlying conditions known to affect intestinal microbiota composition, including cirrhosis, uncontrolled diabetes mellitus, end-stage renal disease, obesity, malignancy, or psychiatric disorders.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Rifaximin (drug)Participants randomized to this arm receive rifaximin 550 mg orally three times daily for 2 weeks. Allocation is randomized and double-blinded. | Drug | Rifaximin |
| PlaceboMatching placebo administered orally three times daily for 14 days. | Drug | Placebo |
Primary outcome
Bloating responder rate
Time frame: From enrollment to the end of treatment at 2 weeks
Bloating responder is defined as at least a 1-point reduction from baseline to week 2 in bloating symptom severity measured using a 7-point Likert scale for bothersomeness of bloating (range 0 to 6; higher scores indicate worse symptoms). Score categories are 0 = not at all, 1 = hardly, 2 = somewhat, 3 = moderately, 4 = a good deal, 5 = a great deal, and 6 = a very great deal.
21 secondary outcomes
Abdominal pain response rate
Time frame: From enrollment to the end of treatment at 2 weeks
Change in Global IBS Symptoms (IBS-C patients)
Time frame: From enrollment to the end of treatment at 2 weeks
Treatment satisfaction
Time frame: End of treatment at 2 weeks
Change in Psychological Symptoms
Time frame: From enrollment to the end of treatment at 2 weeks
Change in Quality of Life (IBS-C patients)
Time frame: From enrollment to the end of treatment at 2 weeks
Change in quality of life (FAB patients)
Time frame: From enrollment to the end of treatment at 2 weeks
Stool microbiota diversity and composition
Time frame: From enrollment to the end of treatment at 2 weeks
Change in intestinal gas measurement (hydrogen)
Time frame: From enrollment to the end of treatment at 2 weeks
Change in intestinal gas measurement (methane)
Time frame: From enrollment to the end of treatment at 2 weeks
Proportion of patients with positive lactulose hydrogen breath test
Time frame: From enrollment to the end of treatment at 2 weeks
Rescue medication use
Time frame: From enrollment to the end of treatment at 2 weeks
Adverse events
Time frame: From enrollment to the end of treatment at 2 weeks
Association between baseline bloating symptom severity score and bloating response at 2 weeks
Time frame: Baseline predictor with treatment response assessed at 2 weeks
Association between baseline fecal microbiota alpha diversity and bloating response at 2 weeks
Time frame: Baseline predictor with treatment response assessed at 2 weeks
Association between baseline positive diagnosis of small intestinal bacterial overgrowth and bloating response at 2 weeks
Time frame: Baseline predictor with treatment response assessed at 2 weeks.
Association between baseline positive diagnosis of intestinal methanogen overgrowth and bloating response at 2 weeks
Time frame: Baseline predictor with treatment response assessed at 2 weeks.
Changes in fecal short-chain fatty acid concentrations
Time frame: From enrollment to the end of treatment at 2 weeks
Changes in plasma bile acid concentrations
Time frame: From enrollment to the end of treatment at 2 weeks
Changes in gut-derived uremic toxin concentrations
Time frame: From enrollment to the end of treatment at 2 weeks
Bloating response at weeks 4
Time frame: From enrollment to 4 weeks
Bloating response at weeks 8
Time frame: From enrollment to 8 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 27 Oct 2026.
- Background: PubMed 27144627Mearin F, Lacy BE, Chang L, Chey WD, Lembo AJ, Simren M, Spiller R. Bowel Disorders. Gastroenterology. 2016 Feb 18:S0016-5085(16)00222-5. doi: 10.1053/j.gastro.2016.02.031. Online ahead of print.
- Background: PubMed 36922331Lacy BE, Chang L, Rao SSC, Heimanson Z, Sayuk GS. Rifaximin Treatment for Individual and Multiple Symptoms of Irritable Bowel Syndrome With Diarrhea: An Analysis Using New End Points. Clin Ther. 2023 Mar;45(3):198-209. doi: 10.1016/j.clinthera.2023.01.010. Epub 2023 Mar 14.
- Background: PubMed 32047534Chey WD, Shah ED, DuPont HL. Mechanism of action and therapeutic benefit of rifaximin in patients with irritable bowel syndrome: a narrative review. Ther Adv Gastroenterol. 2020 Jan 23;13:1756284819897531. doi: 10.1177/1756284819897531. eCollection 2020.
- Background: PubMed 40844856Melchior C, Hammer H, Bor S, Barba E, Horvat IB, Celebi A, Drug V, Dumitrascu D, Kalkan IH, Hauser G, Lionis C, Livovsky D, Mari A, Mulak A, Surdea-Blaga T, Tack J, Vanuytsel T, Savarino EV, Zarate-Lopez N, Hammer J, Dickman R. European Consensus on Functional Bloating and Abdominal Distension-An ESNM/UEG Recommendations for Clinical Management. United European Gastroenterol J. 2025 Nov;13(9):1613-1651. doi: 10.1002/ueg2.70098. Epub 2025 Aug 22.
- Background: PubMed 37452811Moshiree B, Drossman D, Shaukat A. AGA Clinical Practice Update on Evaluation and Management of Belching, Abdominal Bloating, and Distention: Expert Review. Gastroenterology. 2023 Sep;165(3):791-800.e3. doi: 10.1053/j.gastro.2023.04.039. Epub 2023 Jul 13.
- Background: PubMed 37310270Arora U, Sachdeva K, Garg P, Baitha U, Kedia S, Kalaivani M, Ahuja V, Kumar A, Ranjan P, Vikram NK, Sinha S, Biswas A, Wig N. Efficacy of Rifaximin in Patients With Abdominal Bloating or Distension: A Systematic Review and Meta-analysis. J Clin Gastroenterol. 2024 Apr 1;58(4):360-369. doi: 10.1097/MCG.0000000000001872.
- Individual participant dataSharing planned: No. To protect participant confidentiality and comply with institutional and regulatory requirements, no IPD will be shared unless with reasonable request.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Monthira Maneerattanaporn, M.D. principal investigator
Mahidol University
Pubet Weeranawin, M.D. study chair
Mahidol University
Somchai Leelakusolvong, M.D. study chair
Mahidol University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing Rifaximin (drug) in people with Bloating and Rifaximin, run by Mahidol University at 1 site in Thailand.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 27 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Thailand. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Monthira Maneerattanaporn, M.D. (+66 24197281, monthira.man@mahidol.ac.th), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Bloating responder rate (time frame: From enrollment to the end of treatment at 2 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT07522255, which also lists 6 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 27 Oct 2026.