Pepto-Bismol (Bismuth Subsalicylate)
bismuth subsalicylate
Indications for Bismuth Subsalicylate
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Diarrhea (acute, nonspecific) | Adults & children ≥12 y | Symptomatic treatment (OTC) | FDA Approved |
| Upset stomach / indigestion | Adults & children ≥12 y | Symptomatic relief (OTC) | FDA Approved |
| Heartburn | Adults & children ≥12 y | Symptomatic relief (OTC) | FDA Approved |
| Nausea | Adults & children ≥12 y | Symptomatic relief (OTC) | FDA Approved |
| H. pylori eradication (as part of quadruple therapy) | Adults | Component of Helidac Therapy (BSS + metronidazole + tetracycline + antisecretory agent) | FDA Approved (Rx) |
Bismuth subsalicylate has been commercially available for over a century and was first FDA-approved in 1939. Its dual composition as an insoluble bismuth salt and a salicylate confers a unique combination of antimicrobial, antisecretory, anti-inflammatory, and mucosal protective effects. The drug remains a mainstay of OTC gastrointestinal symptom relief and is a critical component of bismuth-based quadruple therapy for H. pylori eradication, which the ACG 2024 guideline now recommends as the preferred first-line regimen for treatment-naive patients.
Traveler’s diarrhea prophylaxis: Two tablets (524 mg) chewed four times daily for up to 3 weeks provides approximately 62–65% protection against traveler’s diarrhea. Efficacy is less than antimicrobial prophylaxis (~80%), and the frequent dosing may limit adherence. (Evidence quality: moderate)
Microscopic colitis (alternative therapy): The AGA conditionally recommends bismuth subsalicylate as an alternative to budesonide for inducing clinical remission in patients with symptomatic microscopic colitis who cannot take budesonide. Typical regimen: 262 mg, 3 tablets TID for 8 weeks. (Evidence quality: low)
Dosing
Adult & Adolescent (≥12 Years) OTC Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Diarrhea / upset stomach / nausea — regular strength (262 mg tabs) | 524 mg (2 tabs) PO | 524 mg q30min–1h PRN | 4,192 mg/day (8 doses) | Chew tablets before swallowing; do not use for >2 days without medical advice Ensure adequate hydration alongside use |
| Diarrhea / upset stomach / nausea — extra strength (525 mg caplets) | 525 mg (1 caplet) PO | 525 mg q30min–1h PRN | 2,100 mg/day (4 doses) | Swallow caplets whole; do not chew |
| Diarrhea / upset stomach — liquid (262 mg/15 mL) | 30 mL PO | 30 mL q30min–1h PRN | 8 doses/day | Shake well before use; measure with provided dosing cup Do not use a household spoon |
| Traveler’s diarrhea — prophylaxis (off-label) | 524 mg (2 tabs) PO QID | 524 mg QID with meals & bedtime | 2,096 mg/day | Continue for duration of travel, up to 3 weeks maximum ~62–65% protection; less effective than antimicrobial prophylaxis |
H. pylori Eradication — Bismuth Quadruple Therapy (Rx)
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| H. pylori — optimised BQT (ACG 2024 guideline) | BSS 524 mg (2 × 262 mg tabs) PO QID | 524 mg QID × 14 days | 2,096 mg/day | Combined with: tetracycline 500 mg QID + metronidazole 500 mg TID–QID + PPI BID ACG 2024: do not substitute doxycycline for tetracycline. 14-day duration preferred. |
| H. pylori — Helidac Therapy pack (FDA-approved) | BSS 525 mg (2 chewable tabs) PO QID | 525 mg QID × 14 days | 2,100 mg/day | Pre-packaged with metronidazole 250 mg QID + tetracycline 500 mg QID; give with antisecretory agent Helidac originally approved with H2RA; ACG now recommends PPI BID instead |
Bismuth subsalicylate releases salicylic acid upon hydrolysis. At the maximum OTC dose of 4,192 mg/day, the salicylate load is roughly equivalent to several standard aspirin doses. Patients concurrently taking aspirin or other salicylates should be warned about additive salicylate toxicity, and tinnitus serves as an early warning sign of excessive salicylate levels. If tinnitus develops, the drug should be discontinued.
Bismuth subsalicylate is not recommended for OTC use in children under 12 years. Due to the salicylate component, it is contraindicated in children and teenagers with or recovering from influenza or varicella because of the association with Reye syndrome.
Pharmacology
Mechanism of Action
Bismuth subsalicylate is an insoluble salt that undergoes acid-catalysed hydrolysis in the stomach, dissociating into two pharmacologically active components: trivalent bismuth salts and salicylic acid. The bismuth component remains largely within the GI lumen, where it exerts direct bactericidal effects against enteropathogens including H. pylori, E. coli, and Campylobacter species by disrupting bacterial cell walls and glycocalyx. Bismuth also forms a protective coating over inflamed or ulcerated mucosa, shields epithelium from pepsin and acid, and stimulates endogenous prostaglandin, mucus, and bicarbonate secretion. The salicylate component is almost completely absorbed and exerts anti-inflammatory and antisecretory effects by inhibiting cyclooxygenase-mediated prostaglandin synthesis in the intestinal mucosa, thereby reducing fluid and electrolyte secretion into the bowel lumen. This dual mechanism provides simultaneous antimicrobial, antisecretory, anti-inflammatory, and cytoprotective actions.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | Salicylate: >80% absorbed from GI tract; Cmax 13.1 μg/mL after 525 mg single dose (fasted); Tmax 1–2 h. Bismuth: <1% absorbed systemically | Salicylate achieves therapeutic plasma levels; bismuth acts locally in GI tract with negligible systemic absorption under normal use |
| Distribution | Bismuth: highly protein bound (>90%); distributed throughout body when absorbed. Salicylate: widely distributed; crosses placenta | Prolonged bismuth tissue retention (weeks); avoid in pregnancy due to salicylate placental transfer |
| Metabolism | Salicylate: hepatic conjugation (glycine and glucuronic acid); saturable (nonlinear kinetics above 525 mg BSS doses); clearance lower in females. Bismuth: not significantly metabolised | Nonlinear salicylate kinetics means disproportionate accumulation at higher or repeated doses; female patients may have higher salicylate exposure |
| Elimination | Salicylate: t½ 2–5 h (single dose); renal excretion. Bismuth: intermediate t½ 5–11 days, terminal t½ 21–72 days; renal clearance ~50 mL/min; also biliary excretion | Bismuth accumulates with prolonged use (risk of neurotoxicity after >6 weeks); salicylate half-life lengthens at high doses due to saturable metabolism |
Side Effects
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Black/darkened stools | >10% | Harmless; caused by bismuth sulfide formation in the GI tract; resolves days after discontinuation; does not interfere with standard faecal occult blood tests |
| Darkened tongue | >10% | Temporary discolouration; resolves spontaneously; caused by bismuth reacting with sulfur in saliva |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Constipation | ~3–7% | Dose-related; more common with prolonged use; reduce dose if bothersome |
| Nausea | ~1–5% | Often difficult to distinguish from the underlying GI condition being treated |
| Tinnitus | ~1–3% | Salicylate effect; serves as an early warning sign of salicylate accumulation; discontinue if develops |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Salicylate toxicity (salicylism) | Rare at recommended doses; risk increases with concurrent salicylates or prolonged use | Days to weeks | Discontinue immediately; check salicylate levels; manage tinnitus, tachypnoea, metabolic acidosis per toxicology protocol |
| Reye syndrome (children/teens) | Very rare; associated with salicylate use during viral illness | Days after viral illness | Emergency care; ICU admission; supportive management of hepatic failure and cerebral oedema |
| Bismuth encephalopathy / neurotoxicity | Very rare; associated with prolonged high-dose use (>6 weeks) | Weeks to months of chronic use | Discontinue bismuth; symptoms (myoclonus, confusion, ataxia, fatigue) are generally reversible upon cessation |
| GI bleeding (exacerbation) | Rare | Variable | Discontinue; evaluate source of bleeding; note that black stools from bismuth can mask true GI bleeding |
Formal discontinuation rate data from controlled trials are limited for OTC bismuth subsalicylate as a standalone product. In the H. pylori quadruple therapy context, discontinuation is more commonly driven by the metronidazole and tetracycline components (GI upset, metallic taste, nausea) than by the bismuth subsalicylate itself. The primary reasons for self-discontinuation in OTC use are constipation, cosmetic concerns (black stools/tongue), and tinnitus.
Bismuth-induced darkening of the stool is harmless and expected. However, it can mask true melena from upper GI bleeding. Clinicians should maintain a low threshold for further investigation if patients on bismuth subsalicylate present with dark stools accompanied by hemodynamic changes, epigastric pain, or haemoglobin decline. Standard faecal occult blood testing is not affected by bismuth.
Drug Interactions
The salicylate component of bismuth subsalicylate accounts for most clinically significant drug interactions. Salicylate inhibits cyclooxygenase, displaces drugs from protein binding, and affects renal prostaglandin synthesis. The bismuth component can chelate tetracycline antibiotics in the GI lumen, reducing their absorption. Paradoxically, in H. pylori quadruple therapy, tetracycline and bismuth subsalicylate are intentionally co-administered; their local antimicrobial synergy outweighs the partial absorption reduction.
Monitoring
-
Symptom Resolution
After 48 h (acute)
Routine If diarrhea persists beyond 2 days of OTC use, discontinue and seek medical evaluation. Persistent symptoms may indicate an infectious or inflammatory cause requiring specific treatment. -
Tinnitus / Hearing
Each visit; patient self-report
Routine Tinnitus indicates salicylate accumulation and mandates immediate discontinuation. Particularly important when BSS is co-administered with aspirin or other salicylates. -
H. pylori Eradication
≥4 weeks after completing BQT
Routine ACG 2024 guideline requires confirmatory test of cure (urea breath test or faecal antigen) at least 4 weeks after completing therapy and at least 2 weeks after stopping PPI. -
Neurological Status
If use exceeds 6 weeks
Trigger-based Prolonged bismuth use can cause encephalopathy (myoclonus, confusion, ataxia). Assess for neurological symptoms if extended use is planned. Symptoms are generally reversible on discontinuation. -
Renal Function
If renal impairment present
Trigger-based Bismuth is renally cleared (clearance ~50 mL/min). In renal impairment, bismuth accumulation increases the risk of neurotoxicity. Avoid prolonged use and monitor renal function.
Contraindications & Cautions
Absolute Contraindications
- Children or teenagers with influenza or varicella — salicylate component associated with Reye syndrome
- Known allergy to salicylates (including aspirin) — cross-reactivity expected
- Active GI bleeding (bloody or black tarry stools not attributed to prior bismuth use)
- Children under 12 years (OTC use) — not recommended without physician guidance
Relative Contraindications (Specialist Input Recommended)
- Concurrent anticoagulant therapy — increased bleeding risk from salicylate component
- Gout — salicylates may decrease urate excretion at low doses, interfering with uricosuric therapy
- Renal impairment — risk of bismuth accumulation and nephrotoxicity with prolonged use
Use with Caution
- Pregnancy — salicylate crosses placenta; chronic use may cause premature ductus arteriosus closure and intrauterine growth restriction; avoid especially in third trimester
- Lactation — salicylate is excreted in breast milk; theoretical risk of Reye syndrome in nursing infants
- Diabetes mellitus — salicylate may potentiate hypoglycaemic agents; monitor blood glucose
- Pre-existing peptic ulcer disease — discuss with prescriber before use; salicylate may exacerbate ulceration
- Concurrent aspirin or NSAID use — additive salicylate load and GI bleeding risk
Products containing salicylates, including bismuth subsalicylate, carry a warning about the association between salicylate use in children and teenagers during viral illnesses (influenza, varicella) and Reye syndrome, a rare but potentially fatal condition causing acute hepatic failure and encephalopathy. Do not administer to children or teenagers who have or are recovering from chickenpox or flu-like symptoms.
Patient Counselling
Purpose of Therapy
Bismuth subsalicylate helps relieve diarrhea, upset stomach, heartburn, indigestion, and nausea. It works by coating the stomach lining, reducing inflammation, decreasing fluid secretion into the bowel, and fighting certain bacteria that cause diarrhea. It does not cure the underlying cause of your symptoms.
How to Take
For regular-strength chewable tablets (262 mg), chew 2 tablets every 30 minutes to 1 hour as needed. For extra-strength caplets (525 mg), swallow 1 caplet whole every 30 minutes to 1 hour as needed. For the liquid form, shake well and use the provided measuring cup. Do not take more than the recommended number of doses in 24 hours. If symptoms last more than 2 days, stop taking the medication and see a healthcare provider.
Sources
- Helidac Therapy (bismuth subsalicylate/metronidazole/tetracycline HCl) — FDA-approved prescribing information (revised 2021). FDA Label Primary regulatory source for BSS pharmacokinetics (salicylate and bismuth), H. pylori dosing, interactions, and adverse effects in the quadruple therapy context.
- Pepto-Bismol (bismuth subsalicylate) OTC product labelling. Procter & Gamble. OTC label with dosing instructions, maximum daily doses, and consumer warnings including Reye syndrome and salicylate interactions.
- Budisak P, Patel P, Abbas M. Bismuth Subsalicylate. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2024. NCBI Bookshelf Comprehensive peer-reviewed summary of indications, mechanism, pharmacokinetics, adverse effects, and monitoring for BSS.
- Gorbach SL. Bismuth therapy in gastrointestinal diseases. Gastroenterology. 1990;99(3):863–875. DOI Foundational review of bismuth’s antimicrobial, cytoprotective, and antisecretory properties across GI conditions including H. pylori and traveler’s diarrhea.
- DuPont HL. Bismuth subsalicylate in the treatment and prevention of diarrheal disease. Drug Intell Clin Pharm. 1987;21(9):687–693. DOI Early clinical review establishing BSS efficacy in both treatment and prophylaxis of traveler’s diarrhea.
- Chey WD, Howden CW, Moss SF, et al. ACG Clinical Guideline: Treatment of Helicobacter pylori Infection. Am J Gastroenterol. 2024;119(9):1730–1753. DOI Current ACG guideline recommending optimised bismuth quadruple therapy as preferred first-line regimen for treatment-naive H. pylori infection.
- Nguyen GC, Smalley WE, Vege SS, et al. American Gastroenterological Association Institute Guideline on the Medical Management of Microscopic Colitis. Gastroenterology. 2016;150(1):242–246. DOI AGA guideline conditionally recommending BSS as an alternative to budesonide for inducing clinical remission in microscopic colitis.
- Pitz AM, Park GW, Lee D, et al. Antimicrobial activity of bismuth subsalicylate on Clostridium difficile, Escherichia coli O157:H7, norovirus, and other common enteric pathogens. Gut Microbes. 2015;6(2):93–100. DOI Demonstrates BSS’s broad-spectrum antimicrobial activity against common enteropathogens in vitro.
- Stratton CW, Warner RR, Coudron PE, Lilly NA. Bismuth-mediated disruption of the glycocalyx-cell wall of Helicobacter pylori: ultrastructural evidence for a mechanism of action for bismuth salts. J Antimicrob Chemother. 1999;43(5):659–666. DOI Ultrastructural study showing bismuth’s direct bactericidal action against H. pylori via glycocalyx disruption.
- Nwokolo CU, Mistry P, Pounder RE. The absorption of bismuth and salicylate from oral doses of Pepto-Bismol (bismuth salicylate). Aliment Pharmacol Ther. 1990;4(2):163–169. DOI Key PK study characterising the absorption profiles of both bismuth and salicylate components following oral BSS administration.
- Graham DY, Estes MK, Gentry LO. Double-blind comparison of bismuth subsalicylate and placebo in the prevention and treatment of enterotoxigenic Escherichia coli-induced diarrhea in volunteers. Gastroenterology. 1983;85(5):1017–1022. Landmark volunteer challenge RCT demonstrating BSS’s efficacy in both prevention and treatment of enterotoxigenic E. coli diarrhea under controlled conditions.
- Sheele J, Cartowski J, Dart A, et al. Saccharomyces boulardii and bismuth subsalicylate as low-cost interventions to reduce the duration and severity of cholera. Pathog Glob Health. 2015;109(6):275–282. DOI Evaluates BSS’s utility in cholera management as a low-cost intervention in resource-limited settings.