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Bismuth Subsalicylate

Also known as: BSS, Subsalicylate of bismuth

An oral antidiarrheal containing salicylate; relief, travel prevention and warning-sign assessment are different decisions.

Cut-paper collage of a closed bottle beside a dish of pale pink liquid
Editorial illustration

Bismuth subsalicylate is an oral medicine for short-term diarrhea relief, with evidence for reducing travelers' diarrhea risk in selected adults. It contains salicylate, so aspirin allergy, bleeding risks and certain medicines matter. Longer prevention studies are not permission to ignore the two-day limit in U.S. diarrhea-treatment labeling.1, 5, 3

  • M008's antidiarrheal labeling limits self-treatment to no more than two days.1
  • CDC notes that travel-prevention safety beyond three weeks has not been established.3
  • Temporary tongue or stool darkening can occur, but pre-existing bloody or black stool is a do-not-use warning.1

What is Bismuth Subsalicylate?

The active ingredient is bismuth subsalicylate, not elemental bismuth or every other bismuth salt. MedlinePlus describes several stomach-symptom uses, while FDA M008 specifically addresses antidiarrheal products. The Drug Facts active, concentration and intended use are more informative than a familiar color or brand name.2, 1

Where it comes from

Natural sources

  • Bismuth is an element; the medicine is a manufactured compound

How it's made

A specified bismuth subsalicylate ingredient is formulated into oral liquid or tablets. Other salts and elemental quantities are not medicine-dose equivalents.

What it does in products

  • Active in oral antidiarrheal medicines
  • Active in some upset-stomach medicines

Benefits

Short-term diarrhea symptom relief

moderate evidence

Controlled evidence and OTC conditions support symptom relief, not treatment of every pathogen or replacement of rehydration.4, 6, 1

The 2021 review pooled older infectious-diarrhea studies and included several manufacturer-employed authors. A separate 439-person analysis in Pakistan found less antibiotic use but no detected difference in time to resolution, showing that outcomes and settings matter.

Travelers' diarrhea prevention in selected adults

moderate evidence

Trials suggest a reduction in risk, but suitability and the burden of repeated use limit its role.5, 3

The 2024 network review assessed 31 trials across several interventions, not 31 bismuth trials. It judged the bismuth-versus-placebo comparison moderate confidence and reported more adverse events with bismuth; this is not a recommendation for every traveler.

Evidence scope and limitations

Oral bismuth subsalicylate for short-term diarrhea and selected-adult travel prevention; not every bismuth salt or H. pylori combination regimen.

  • Some pooled trials are old, with subjective outcomes and manufacturer involvement.
  • The network review combines different interventions and destinations; not every included participant received bismuth.
  • The 2019 primary abstract supports its reported endpoints, not an unreported faster-recovery effect.
  • Prevention-study duration does not override treatment labeling, and neither setting clears high-risk age, pregnancy or medicine combinations.

Evidence last checked: 2026-10-11

Side effects & safety

Tongue or stool darkening, constipation or nausea (varies)Darkening after use may be temporary and harmless, but do not assume bleeding-related stool changes have the same cause.
Ringing ears or hearing changes (varies)FDA labeling requires stopping and seeking advice for these symptoms; salicylate exposure is relevant.

Safety considerations

  • CDC does not recommend bismuth subsalicylate in pregnancy. MedlinePlus advises discussing breastfeeding with a clinician.
  • Do not combine with other salicylate products. Anticoagulants and medicines for diabetes, gout or arthritis require a clinician or pharmacist check.
  • CDC additionally flags methotrexate and probenecid; tetracycline-antibiotic timing requires checking with a pharmacist.
  • Not for: Avoid self-use with aspirin/salicylate allergy, ulcer, bleeding problems or bloody/black stool; fever or mucus in stool needs assessment.
  • Not for: CDC excludes renal insufficiency and gout from travel-prophylaxis use. Children and teenagers with viral illness face a Reye syndrome warning; this is not an infant diarrhea remedy.
  • Not for: Worsening symptoms, dehydration or diarrhea beyond two days should not be managed by simply extending the course.
1, 2, 3

Amounts studied & product use

These figures describe research or common product use, not a personal dose or treatment recommendation.

In supplement studies and products

This is a medicine, not a supplement dose. M008 describes 525 mg at 30–60-minute intervals or 1,050 mg hourly as needed for ages 12 and over, with a 4,200 mg/24-hour ceiling and no more than two days for diarrhea. These are regulatory label conditions, not personal instructions; liquid strength and tablets differ. Follow the actual label and obtain advice about travel prophylaxis rather than repurposing this schedule.

1, 3

Regulatory status

  • FDA M008 includes bismuth subsalicylate as an OTC oral antidiarrheal under its full active-ingredient, labeling and general drug conditions. Its treatment label is not blanket authorization for chronic use or every advertised prevention claim.
1

Do not confuse a harmless color change with a bleeding warning

FDA's same monograph describes temporary darkening after use and says not to use the medicine when stool is already bloody or black. Timing and the surrounding symptoms are essential; the harmless-effect statement should not be used to dismiss possible bleeding.

Our reading: decide first whether this is uncomplicated short-term symptom relief, a professionally considered prevention plan or an illness needing assessment. A trial measuring lower antibiotic use did not show faster resolution in that setting, and none makes oral hydration optional.

1, 2, 6, 3

Frequently asked questions

Does the three-week prevention evidence permit longer diarrhea self-treatment?

No. Prevention and treatment are different settings. U.S. antidiarrheal labeling says no more than two days, and CDC says safety beyond three weeks of prevention is unestablished.1, 3

Is it suitable when someone has aspirin allergy?

The active contains salicylate. FDA's allergy warning excludes salicylate allergy, including aspirin, and concurrent salicylate products; the word bismuth does not remove that warning.1

The bottom line

Read the salicylate warnings and intended-use duration before the reassuring pink-liquid image; symptom relief is not a diagnosis or a chronic-use clearance.

References

  1. OTC Monograph M008: Antidiarrheal Drug Products for OTC Human Use. U.S. Food and Drug Administration (2022) · government guidance · M008; OTC000022; posted April 4, 2022
  2. Bismuth Subsalicylate: Drug Information. MedlinePlus / AHFS Consumer Medication Information (2016) · ingredient monograph · Revised August 15, 2016; read with current FDA and CDC guidance
  3. Connor BA, Leung DT. Travelers’ Diarrhea. CDC Yellow Book, 2026 edition (2026) · government guidance · Chapter updated March 24, 2026
  4. Brum JM, Gibb RD, Ramsey DL, Balan G, Yacyshyn BR. Systematic Review and Meta-Analyses Assessment of the Clinical Efficacy of Bismuth Subsalicylate for Prevention and Treatment of Infectious Diarrhea. Digestive Diseases and Sciences (2021) · systematic review · PMID 32772204; DOI 10.1007/s10620-020-06509-7; online 2020, journal issue 2021; primary abstract assessment
  5. Fan H, Liu IC, Gao L, Wu L. Bismuth subsalicylate, probiotics, rifaximin and vaccines for the prevention of travelers’ diarrhea: a systematic review and network meta-analysis. Frontiers in Pharmacology (2024) · meta analysis · PMID 38698820; DOI 10.3389/fphar.2024.1361501
  6. Bowen A, Agboatwalla M, Pitz A, Salahuddin S, Brum J, Plikaytis B. Effect of Bismuth Subsalicylate vs Placebo on Use of Antibiotics Among Adult Outpatients With Diarrhea in Pakistan: A Randomized Clinical Trial. JAMA Network Open (2019) · randomized trial · PMID 31418805; DOI 10.1001/jamanetworkopen.2019.9441; NCT02047162; primary abstract assessment

Revision history

  1. Initial AI-assisted source checks and claim-level citation mapping under the site-authorized publishing workflow. No separate human or independent medical review is claimed.