Healthy AdultsPhase 1NCT05930197
Effect of Bismuth Subsalicylate on the Gut Microbiome and Host Response in Healthy Adults
A Phase 1 study testing Bismuth subsalicylate in people with Healthy Adults, run by National Institute of Allergy and Infectious Diseases (NIAID) at 1 site in United States.
Trial summary
Background: Many kinds of good or normal bacteria live on your skin and inside your stomach and intestines (gut). These bacteria are important to your health. What you eat, where you live, and what medicines you take can affect the bacteria in your gut. Read more about this study
- Who is it for?
- Ages 18 to 50 years
- Conditions the study is for
- Healthy Adults
- What is being tested?
- Bismuth subsalicylate
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 34 participants
- Where
- 1 siteUnited States
- Study dates
- 31 Aug 2023to 15 Dec 2024
- Phase
- Phase 1
- Are there results?
- Yes, posted in the registrySummary in the doctors' view
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 50 years
- All sexes
- No healthy volunteers
- Adult
Who may be able to join
- An individual must meet all the following criteria to be eligible for this study:
- Aged 18 to 50 years.
- In generally good health.
- Able to provide informed consent.
- Willing to allow samples and data to be stored and shared for future research.
- Participants who can become pregnant must agree to use one effective method of contraception when engaging in sexual activities that can result in pregnancy, beginning at the signing of the informed consent form (as early as week -18) until the final study visit. Acceptable methods of contraception include the following:
Show all 10Show fewer
- External or internal condom with spermicide.
- Diaphragm or cervical cap with a spermicide.
- Hormonal contraception.
- Intrauterine device.
Who cannot join
- An individual who meets any of the following criteria will be excluded from participation in this study:
- Use of systemic antibiotics in the last 3 months.
- BSS use in the last 3 months.
- Pregnant or breastfeeding.
- Allergy to BSS.
- Allergy to other salicylates (including aspirin).
Show all 17Show fewer
- Current use of other salicylates (including aspirin).
- Current use of anticoagulant medications.
- History of or active GI ulcers.
- History of or active bleeding disorder.
- Bloody stool within the last 3 months.
- Diarrhea within the last 2 weeks (defined as three or more loose or liquid stools per day).
- Current use of medications that may have a drug interaction with BSS.
- Not proficient in written English.
- Currently participating in another clinical trial that may affect current study procedures, per investigator s discretion.
- Any condition that, in the opinion of the study team, contraindicates participation in this study.
- Co-enrollment in other studies is restricted. Consideration for co-enrollment in clinical trials evaluating the use of a licensed medication will require the approval of the principal investigator. Study staff should be notified of co-enrollment on any other protocol as it may require the approval of the principal investigator.
Trial locations and contacts
1 site in 1 country.
United States1 site
National Institutes of Health Clinical Center
Bethesda, Maryland, 20892
About this study
Official title: An Exploratory Study of The Effect of Bismuth Subsalicylate on The Gut Microbiome and Host Response in Healthy Adults
Background:
Many kinds of good or normal bacteria live on your skin and inside your stomach and intestines (gut). These bacteria are important to your health. What you eat, where you live, and what medicines you take can affect the bacteria in your gut. Bismuth subsalicylate (BSS) is an ingredient in common medicines for mild diarrhea and stomach pain. Products that contain BSS include Pepto-Bismol, Kao-Tin, and Pink Bismuth. But how BSS affects the bacteria in a person s gut is not fully understood.
Read more
Objective:
To see how BSS affects gut bacteria in healthy people.
Eligibility:
Healthy people aged 18 to 50 years.
Design:
Participants will have 6 clinic visits in up to 18 weeks. Only 1 visit must be at the NIH clinic; others may be either in-person or remote.
BSS is a liquid taken by mouth. Participants will take a dose of BSS 4 times a day for 2 days. They will take the same amount of BSS as a person would take to treat diarrhea or related problems.
Stool samples will be collected at each study visit. For remote visits, participants will be given a collection kit; they will collect the sample at home and send it in.
Participants will take surveys at each visit. They will answer questions about their diet and health.
Participants may also provide optional samples of blood, saliva, and urine.
Participants may have up to 2 optional colonoscopies. A long tube will be inserted via the rectum to collect tissue samples from the intestine. Participants will be sedated or placed under anesthesia for the procedure.
Read the detailed description
Study Description:
This is a single-site, single-arm, open-label study to evaluate the effect of bismuth subsalicylate (BSS) on the human gut microbiome and host immune response. Upon confirmation of eligibility, healthy adult volunteers will provide stool and optional blood, saliva, urine, and intestinal biopsy samples for a baseline assessment of gut microbiome and host immune response. Up to 18 weeks later, participants will undergo a 2-day/8-dose regimen of oral BSS. Stool will be collected at baseline, days 2 (+3), 8 (+/-3), 14 (-3/+7) and 28 (+/-7). Blood, saliva, and urine are also optional at these time points. Participants may also undergo a second optional colonoscopy at day 8 (+/-3) to provide colon biopsies for research analysis.
Primary Objective:
To evaluate the effect of BSS on the human gut microbiome.
Secondary Objective:
To evaluate the effect of BSS on the human gut metabolome.
Tertiary/Exploratory Objective:
To evaluate the effect of BSS on the systemic and intestinal host response (immune and inflammatory responses).
Primary Endpoint:
Differences in the relative abundance of taxa in stool samples pre-BSS and approximately 1 month post-BSS. Differences in microbiome metrics of alpha diversity and beta diversity will also be assessed.
Secondary Endpoint:
Differences in the stool metabolome (including short chain fatty acids, bile acids, and untargeted metabolomics) pre-BSS and approximately 1 month post-BSS.
Tertiary/Exploratory Endpoint:
Differences in systemic host immune and inflammatory responses, such as cytokines and immune cells, and host intestinal immune responses, such as specific T-cell populations in intestinal biopsies pre-BSS and approximately 1 month post-BSS.
- Conditions
- Healthy Adults
- Being tested
- Bismuth subsalicylate
- Keywords
- Intestine, Gut, Metabolites, Microbiota
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Bismuth subsalicylateDrug
BSS is a commonly used, widely available, OTC medication for a variety of gastrointestinal GI symptoms. It is available in the generic form, but also under the more commonly known brands: Bismatrol; Diotame; Geri-Pectate; Kao-Tin; Peptic Relief; Pepto-Bismol; Pink Bismuth and Stomach Relief. It received approval by the US Food and Drug Administration (FDA) in 1939.
| Study group | Role | What they receive |
|---|---|---|
| Interventional | Experimental | The oral suspension formulation of BSS will be used in this study. It is self administered at 1050mg 4 times per day (1 to 6 hours apart) for 2 days. Receives: Drug: Bismuth subsalicylate |
What is being measured
The primary outcome is the main question the study is designed to answer.
To Evaluate the Effect of BSS on the Human Gut Microbiome.
In the context of gut microbiome analysis, this measure represents the number of bacterial taxa that are significantly different between the two timepoints (baseline and 28 days post BSS) based on the read counts which represent abundance of taxa.
We used shotgun metagenomic sequencing to analyze the gut microbiome. Sequenced reads were mapped to a reference database, and the read count abundance of each taxon was calculated. Statistical analysis was performed to identify the number of taxa that are significantly different between timepoints.
Measured: Through Day 28
To Evaluate the Effect of BSS on the Human Gut Microbiome.
Difference of alpha diversity stool samples by Shannon index at baseline (before study drug administration) and 28 days after BSS.
In the context of gut microbiome analysis, the Shannon Index represents a measure of alpha diversity (measure of diversity of a microbial community). The Shannon Index is a value greater than 0 with lower values indicating lower diversity and higher values indicating higher diversity, generally between 1.5 and 3.5, and usually < 4.5. To evaluate changes in the gut microbiome, we compared the mean change in the Shannon Index at baseline and 28 days post-BSS. Shotgun metagenomic sequencing was performed, and sequenced reads were mapped to a reference database to identify and enumerate based on read count unique taxa present in each sample. Statistical analysis was then used to determine whether there were significant differences in the Shannon Index between the two timepoints, providing insight into shifts in microbial diversity following BSS administration.
Measured: Through Day 28.
To Evaluate the Effect of BSS on the Human Gut Microbiome.
Difference of beta diversity stool samples at baseline (before study drug administration) and 28 days after BSS.
Beta diversity refers to the variation in bacterial composition among samples, which we measured utilizing the Bray-Curtis dissimilarity Index. The Bray-Curtis is a widely used metric to quantify beta diversity, reflecting the degree of dissimilarity between samples, and its range is from 0 to 1, with 0 meaning no differences and 1 meaning completely dissimilar. This measure is essential for understanding changes in the bacterial composition over time.
We used shotgun metagenomic sequencing to analyze the gut microbiome. Sequenced reads were mapped to a reference database, and the abundance of each taxon was calculated. The Bray-Curtis dissimilarity index was then calculated using read counts per species per sample to quantify the differences in community composition between samples at baseline and 28 days post-BSS administration.
Measured: Through Day 28.
Secondary outcomes (1)
To Evaluate the Effect of BSS on the Human Gut Metabolome.
In the context of stool metabolome analysis, the number of differentially abundant metabolites refers to the count of metabolites whose levels significantly differ between baseline and 28 days post-BSS. To determine this, we performed broad targeted metabolomic profiling of stool samples collected at both timepoints. Metabolites were identified and quantified, and significant changes in abundance were calculated. The total number of differentially abundant metabolites provides a measure of the metabolic shifts in the gut environment following BSS administration.
Measured: Through Day 28
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted5 Jul 2023
- Study start31 Aug 2023
- Primary completion15 Dec 2024
- Study completion15 Dec 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Other trials for Healthy AdultsStudies of the same condition, open and under way.
- More trials run by National Institute of Allergy and Infectious Diseases (NIAID)The 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 1
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 34 participants (actual)
Sponsor and investigators
- Sponsor type
- US National Institutes of Health
- Responsible party
- Sponsor
- Investigators
- Suchitra K Hourigan, M.D., Principal investigator, National Institute of Allergy and Infectious Diseases (NIAID)
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05930197
- Sponsor's protocol ID
- 10001631
- Other IDs
- 001631-I
- Status last verified
- Mar 2026
- First submitted
- 1 Jul 2023
- Last updated
- 24 Mar 2026
- Results posted
- Yes, on ClinicalTrials.gov
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 24 Mar 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- An Exploratory Study of The Effect of Bismuth Subsalicylate on The Gut Microbiome and Host Response in Healthy Adults
- ClinicalTrials.gov ID
- NCT05930197
- Acronym / sponsor ID
- 10001631
- Conditions
- Healthy Adults
- Keywords
- Intestine, Gut, Metabolites, Microbiota
- Phase
- Phase 1
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 34 participants (actual)
- Lead sponsor
- National Institute of Allergy and Infectious Diseases (NIAID)US National Institutes of Health
- Study start
- 31 Aug 2023 (actual)
- Primary completion
- 15 Dec 2024 (actual)
- Study completion
- 15 Dec 2024 (actual)
- First posted
- 5 Jul 2023 (actual)
- Results
- Posted 24 Mar 2026
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Background:
Many kinds of good or normal bacteria live on your skin and inside your stomach and intestines (gut). These bacteria are important to your health. What you eat, where you live, and what medicines you take can affect the bacteria in your gut. Bismuth subsalicylate (BSS) is an ingredient in common medicines for mild diarrhea and stomach pain. Products that contain BSS include Pepto-Bismol, Kao-Tin, and Pink Bismuth. But how BSS affects the bacteria in a person s gut is not fully understood.
Objective:
To see how BSS affects gut bacteria in healthy people.
Eligibility:
Healthy people aged 18 to 50 years.
Design:
Participants will have 6 clinic visits in up to 18 weeks. Only 1 visit must be at the NIH clinic; others may be either in-person or remote.
BSS is a liquid taken by mouth. Participants will take a dose of BSS 4 times a day for 2 days. They will take the same amount of BSS as a person would take to treat diarrhea or related problems.
Stool samples will be collected at each study visit. For remote visits, participants will be given a collection kit; they will collect the sample at home and send it in.
Participants will take surveys at each visit. They will answer questions about their diet and health.
Participants may also provide optional samples of blood, saliva, and urine.
Participants may have up to 2 optional colonoscopies. A long tube will be inserted via the rectum to collect tissue samples from the intestine. Participants will be sedated or placed under anesthesia for the procedure.
Detailed description
Study Description:
This is a single-site, single-arm, open-label study to evaluate the effect of bismuth subsalicylate (BSS) on the human gut microbiome and host immune response. Upon confirmation of eligibility, healthy adult volunteers will provide stool and optional blood, saliva, urine, and intestinal biopsy samples for a baseline assessment of gut microbiome and host immune response. Up to 18 weeks later, participants will undergo a 2-day/8-dose regimen of oral BSS. Stool will be collected at baseline, days 2 (+3), 8 (+/-3), 14 (-3/+7) and 28 (+/-7). Blood, saliva, and urine are also optional at these time points. Participants may also undergo a second optional colonoscopy at day 8 (+/-3) to provide colon biopsies for research analysis.
Primary Objective:
To evaluate the effect of BSS on the human gut microbiome.
Secondary Objective:
To evaluate the effect of BSS on the human gut metabolome.
Tertiary/Exploratory Objective:
To evaluate the effect of BSS on the systemic and intestinal host response (immune and inflammatory responses).
Primary Endpoint:
Differences in the relative abundance of taxa in stool samples pre-BSS and approximately 1 month post-BSS. Differences in microbiome metrics of alpha diversity and beta diversity will also be assessed.
Secondary Endpoint:
Differences in the stool metabolome (including short chain fatty acids, bile acids, and untargeted metabolomics) pre-BSS and approximately 1 month post-BSS.
Tertiary/Exploratory Endpoint:
Differences in systemic host immune and inflammatory responses, such as cytokines and immune cells, and host intestinal immune responses, such as specific T-cell populations in intestinal biopsies pre-BSS and approximately 1 month post-BSS.
Study design
- Primary purpose
- Basic science
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Interventional | Experimental | Drug: Bismuth subsalicylateThe oral suspension formulation of BSS will be used in this study. It is self administered at 1050mg 4 times per day (1 to 6 hours apart) for 2 days. |
Who may qualify
- Ages
- 18 to 50 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult
Key inclusion criteria (10 listed)
- Aged 18 to 50 years.
- In generally good health.
- Able to provide informed consent.
- Willing to allow samples and data to be stored and shared for future research.
- Participants who can become pregnant must agree to use one effective method of contraception when engaging in sexual activities that can result in pregnancy, beginning at the signing of the informed consent form (as early as week -18) until the final study visit. Acceptable methods of contraception include the following:
Key exclusion criteria (17 listed)
- An individual who meets any of the following criteria will be excluded from participation in this study:
- Use of systemic antibiotics in the last 3 months.
- BSS use in the last 3 months.
- Pregnant or breastfeeding.
- Allergy to BSS.
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 |
|---|---|---|
| Bismuth subsalicylateBSS is a commonly used, widely available, OTC medication for a variety of gastrointestinal GI symptoms. It is available in the generic form, but also under the more commonly known brands: Bismatrol; Diotame; Geri-Pectate; Kao-Tin; Peptic Relief; Pepto-Bismol; Pink Bismuth and Stomach Relief. It received approval by the US Food and Drug Administration (FDA) in 1939. | Drug | Interventional |
Primary outcome
To Evaluate the Effect of BSS on the Human Gut Microbiome.
Time frame: Through Day 28
In the context of gut microbiome analysis, this measure represents the number of bacterial taxa that are significantly different between the two timepoints (baseline and 28 days post BSS) based on the read counts which represent abundance of taxa. We used shotgun metagenomic sequencing to analyze the gut microbiome. Sequenced reads were mapped to a reference database, and the read count abundance of each taxon was calculated. Statistical analysis was performed to identify the number of taxa that are significantly different between timepoints.
To Evaluate the Effect of BSS on the Human Gut Microbiome.
Time frame: Through Day 28.
Difference of alpha diversity stool samples by Shannon index at baseline (before study drug administration) and 28 days after BSS. In the context of gut microbiome analysis, the Shannon Index represents a measure of alpha diversity (measure of diversity of a microbial community). The Shannon Index is a value greater than 0 with lower values indicating lower diversity and higher values indicating higher diversity, generally between 1.5 and 3.5, and usually < 4.5. To evaluate changes in the gut microbiome, we compared the mean change in the Shannon Index at baseline and 28 days post-BSS. Shotgun metagenomic sequencing was performed, and sequenced reads were mapped to a reference database to identify and enumerate based on read count unique taxa present in each sample. Statistical analysis was then used to determine whether there were significant differences in the Shannon Index between the two timepoints, providing insight into shifts in microbial diversity following BSS administration.
To Evaluate the Effect of BSS on the Human Gut Microbiome.
Time frame: Through Day 28.
Difference of beta diversity stool samples at baseline (before study drug administration) and 28 days after BSS. Beta diversity refers to the variation in bacterial composition among samples, which we measured utilizing the Bray-Curtis dissimilarity Index. The Bray-Curtis is a widely used metric to quantify beta diversity, reflecting the degree of dissimilarity between samples, and its range is from 0 to 1, with 0 meaning no differences and 1 meaning completely dissimilar. This measure is essential for understanding changes in the bacterial composition over time. We used shotgun metagenomic sequencing to analyze the gut microbiome. Sequenced reads were mapped to a reference database, and the abundance of each taxon was calculated. The Bray-Curtis dissimilarity index was then calculated using read counts per species per sample to quantify the differences in community composition between samples at baseline and 28 days post-BSS administration.
1 secondary outcome
To Evaluate the Effect of BSS on the Human Gut Metabolome.
Time frame: Through Day 28
Results and safety
Loading the posted results from ClinicalTrials.gov…
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Mar 2026.
- Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
- NIH Clinical Center Detailed Web PageLink provided by the sponsor.
- Individual participant dataSharing planned: No
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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. This study is not recruiting at the moment.
Suchitra K Hourigan, M.D. principal investigator
National Institute of Allergy and Infectious Diseases (NIAID)
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 1 study testing Bismuth subsalicylate in people with Healthy Adults, run by National Institute of Allergy and Infectious Diseases (NIAID) at 1 site in United States.
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 10 inclusion and 17 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: finished, as of the sponsor's last update on 24 Mar 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 United States. 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. 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 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
Yes. Results are posted in the registry (first posted 24 Mar 2026). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
To Evaluate the Effect of BSS on the Human Gut Microbiome. (time frame: Through Day 28). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
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 24 Mar 2026.