Pepto-Bismol (bismuth subsalicylate)

Generic Name: Bismuth Subsalicylate
Brand Name: Pepto-Bismol
Other Brands: Bismatrol, Kaopectate (in some formulations), Pink Bismuth

Drug Class: Gastrointestinal agent; Antidiarrheal; Anti-inflammatory; Antacid
Pharmaceutical Category: OTC (Over-the-Counter) Digestive Remedy
Formulations:
– Oral suspension (liquid)
– Chewable tablets
– Swallowable caplets
Route of Administration: Oral

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1. Pharmacological Classification

Pepto-Bismol (bismuth subsalicylate) is a salicylate-containing bismuth compound with antidiarrheal, anti-inflammatory, and antimicrobial properties. It is available as an over-the-counter (OTC) product and is widely used in self-care for gastrointestinal upset.

This compound is structurally related to both bismuth salts (e.g., bismuth subcitrate) and salicylic acid (the active component in aspirin), combining mild antiseptic and anti-secretory properties.

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2. Mechanism of Action

Bismuth subsalicylate exerts multi-mechanistic effects in the gastrointestinal tract:

A. Antidiarrheal Action

• Salicylate component reduces intestinal inflammation by inhibiting prostaglandin synthesis, leading to decreased intestinal hypermotility and fluid secretion.

• Bismuth has mild bactericidal activity, especially against pathogens like Helicobacter pylori, Escherichia coli, and Salmonella.

B. Antisecretory and Antacid Effects

• Reduces gastric acid secretion and enhances mucosal protection.

• May bind to bacterial toxins (e.g., cholera toxin), neutralizing their effect in the gut.

C. Antimicrobial Activity

• Bismuth precipitates proteins and forms protective coatings over ulcers and erosions.

• Acts synergistically with antibiotics to eradicate H. pylori in multidrug regimens.

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3. Therapeutic Indications

A. Over-the-Counter Uses

• Relief of upset stomach, indigestion, and nausea

• Diarrhea (acute, traveler’s diarrhea, nonspecific)

• Heartburn and acid indigestion

• Gas and bloating

• Bismuth subsalicylate is not intended for chronic diarrhea or severe abdominal conditions.

B. Prescription or Multidrug Use

• Peptic ulcer disease: As part of quadruple therapy for H. pylori eradication

• Traveler’s diarrhea prevention (off-label): Multiple doses daily during travel

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4. Dosage and Administration

Adults and Children ≥12 years

Liquid suspension:

• 30 mL (2 tablespoons) every 30–60 minutes as needed

• Maximum: 240 mL/day (8 doses)

Chewable tablets or caplets:

• 2 tablets every 30–60 minutes as needed

• Maximum: 8 doses (16 tablets) per 24 hours

Duration:

• Short-term use only (≤2 days)

• Seek medical advice if symptoms persist >48 hours

Children <12 years

• Not recommended due to risk of Reye’s syndrome (salicylate-related toxicity)

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5. Pharmacokinetics

• Absorption: Limited systemic absorption of bismuth; salicylate is absorbed in the GI tract

• Metabolism: Salicylate is metabolized hepatically to salicyluric acid

• Excretion:

  • Bismuth excreted in feces

  • Salicylate eliminated via kidneys

• Half-life: Salicylate ~2–4 hours (in normal doses)

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6. Contraindications

• Allergy to salicylates (e.g., aspirin, diflunisal)

• Active GI bleeding or ulceration

• Hemophilia or bleeding disorders

• Severe renal impairment

• Children/teens recovering from viral illness (risk of Reye’s syndrome)

• Pregnancy (3rd trimester) or lactation (salicylate transfer)

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7. Warnings and Precautions

• Reye’s Syndrome Risk: Salicylate toxicity in children/teens recovering from flu or chickenpox

• Black tongue and black stools: Harmless side effect due to bismuth sulfide formation

• Confusion with melena: Important not to misinterpret black stool as GI bleed

• Salicylate toxicity: High doses or prolonged use may lead to tinnitus, metabolic acidosis, or CNS disturbances

• Renal insufficiency: Accumulation of salicylates or bismuth

• Coagulopathy: Prolonged bleeding time possible in patients on anticoagulants

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8. Adverse Effects

Common (≥1%)

• Black discoloration of tongue and stool

• Mild nausea

• Constipation

• Temporary tinnitus (especially with higher doses)

Less Common (0.1–1%)

• Dizziness

• Anxiety

• Bloating or flatulence

Rare (<0.1%)

• Hypersensitivity reactions (rash, angioedema)

• Salicylate toxicity (especially in overdose)

• Reye’s syndrome (inappropriate pediatric use)

• Neurotoxicity (encephalopathy with very high bismuth doses)

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9. Drug Interactions

A. Anticoagulants (e.g., warfarin)

• Additive bleeding risk due to salicylate-mediated platelet inhibition

B. Aspirin and NSAIDs

• Increased salicylate burden; enhanced risk of GI bleeding or salicylism

C. Methotrexate

• Decreased renal clearance → increased toxicity risk

D. Tetracyclines and Quinolones

• Bismuth may impair absorption of antibiotics; avoid coadministration

E. Antidiabetic agents (e.g., sulfonylureas)

• Enhanced hypoglycemic risk via salicylate potentiation

F. Probenecid and Sulfinpyrazone

• May reduce uricosuric effect

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10. Pregnancy and Lactation

Pregnancy

• Avoid, especially in third trimester due to:

  • Risk of premature ductus arteriosus closure (salicylate effect)

  • Potential fetal bleeding

Lactation

• Small amounts of salicylate may enter breast milk

• Use with caution or consider alternative antidiarrheal agents (e.g., loperamide)

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11. Toxicity and Overdose

Symptoms of Salicylate Toxicity (Salicylism):

• Tinnitus, vertigo

• Nausea, vomiting

• Hyperventilation (respiratory alkalosis)

• Metabolic acidosis

• Confusion, agitation

• Seizures or coma (severe cases)

Management

• Discontinue drug immediately

• Supportive care (fluids, electrolyte balance)

• Activated charcoal (if early ingestion)

• Alkalinization of urine (enhance salicylate elimination)

• Hemodialysis in severe cases

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12. Comparison with Related Agents

Property	Pepto-Bismol (Bismuth Subsalicylate)	Loperamide (Imodium)	Bismuth Subcitrate Potassium
Class	Antidiarrheal, Anti-inflammatory	Opioid receptor agonist	Bismuth salt (acid-stable)
Antibacterial	Yes (mild, local GI)	No	Yes (used in H. pylori therapy)
CNS Effects	Minimal	May cause drowsiness	Minimal
Use in Children	Avoid <12 years	Safe >6 years (with caution)	Prescription only
Black stool/tongue	Yes	No	Yes

13. Brand Formulations and Products

Pepto-Bismol (U.S., Global)

• Liquid Suspension: 30 mL/dose (pink, cherry-flavored)

• Chewable Tablets: 262 mg/tablet

• Caplets: Swallowable tablets

Bismatrol, Kaopectate (older formulations)

• Bismuth subsalicylate may be labeled under different brand names regionally

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14. Clinical Notes and Pearls

• Not effective for infectious diarrhea caused by invasive pathogens (e.g., Shigella, Campylobacter)

• Avoid chronic use, especially in elderly or renal-compromised individuals

• Effective in traveler's diarrhea prophylaxis: 2 tablets four times daily (off-label)

• May be used in H. pylori eradication regimens alongside metronidazole and tetracycline (e.g., Pylera)

• Avoid coadministration with live oral vaccines, especially oral cholera vaccine