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Bismuth salt (anti-diarrhoeal / antacid) Pregnancy: There are no adequate data concerning the use of Pepto-Bismol in pregnant women. Animal studies are insufficient with respect to effects on pregnancy, embryonal/foetal development, parturition and postnatal development, and the potential risk for humans is unknown. Pepto-Bismol should not be used during pregnancy and breastfeeding unless the potential benefit outweighs the risks.

Bismuth subsalicylate

Brand names: Pepto-Bismol

Bismuth subsalicylate is used for the symptomatic relief of dyspepsia, mild diarrhoea and nausea, and forms part of some Helicobacter pylori eradication regimens.

Adult dose

Dose: Symptomatic relief of heartburn, indigestion, nausea and upset stomach (due to overindulgence in food and drink); also controls diarrhoea. Pepto-Bismol 17.5 mg/ml oral suspension (each ml contains 17.5 mg bismuth subsalicylate; one 30 ml dose contains 525 mg): adults and adolescents aged 16 years and over, 30 ml in the dosing cup provided; repeat the dose every half hour to 1 hour if needed; no more than 8 doses in 24 hours.
Route: Oral (shake the bottle before use; can be taken before or after meals, on an empty or full stomach)
Frequency: Repeat every half hour to 1 hour if needed
Max: No more than 8 doses (each dose 30 ml) in 24 hours
SCOPE - PINNED PRODUCT ONLY: PEPTO-BISMOL 17.5MG/ML ORAL SUSPENSION (MHRA PL001290358, Procter & Gamble (Health & Beauty Care) Ltd.). Other bismuth subsalicylate products (for example chewable tablets) are not covered. This SPC covers symptomatic relief of heartburn, indigestion, nausea and upset stomach due to overindulgence, and control of diarrhoea only; it gives no travellers' diarrhoea prophylaxis regimen and no Helicobacter pylori regimen, so none is stated. Duration (section 4.4): do not use for more than 2 days except on the advice of a doctor; stop if symptoms get worse, last more than 2 days, or ringing in the ears (tinnitus) appears. Use at doses higher than recommended or for prolonged periods is associated with an increased risk of severe side effects (notably bismuth and salicylate intoxication). Children: contraindicated in children under 16 years of age (possible association between salicylates and Reye's syndrome, particularly in those who have or are recovering from a viral infection such as chicken pox or flu). In diarrhoea, especially in frail and elderly patients, fluid and electrolyte depletion may occur and appropriate fluid and electrolyte replacement is the most important measure.

Dose adjustments

Renal

Not stated - the SPC gives no renal-impairment dosing statement.

Hepatic

Not stated - the SPC gives no hepatic-impairment dosing statement.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to bismuth subsalicylate or to any of the excipients
  • Hypersensitivity to aspirin or other salicylates
  • Concomitant treatment with aspirin or other salicylates
  • Peptic ulcer
  • Blood clotting disorders
  • Bloody or black stool
  • Children under 16 years of age

Side effects

  • Black stool (very common, about 15%): benign and transient blackening of the faeces
  • Black tongue (common, about 8%): benign and transient discoloration of the surface of the tongue
  • Contains the colouring amaranth (E 123), which may cause allergic-type reactions including asthma
  • Doses higher than recommended or prolonged use: risk of severe side effects, notably bismuth and salicylate intoxication
  • Fluid and electrolyte depletion may occur in patients with diarrhoea, especially frail and elderly patients

Interactions

  • Aspirin or other salicylates: do not use together, because of the risk of overdose and salicylate toxicity
  • Anticoagulant therapy: concomitant use may increase the risk and severity of bleeding
  • Medicines for gout (e.g. probenecid, sulfinpyrazone): may increase the risk of hyperuricaemia and worsening gout
  • Sulfonylurea medicines for diabetes (e.g. chlorpropamide, glibenclamide): may increase the risk of hypoglycaemia
  • Medicines for arthritis (e.g. methotrexate): potential drug interactions
  • Tetracycline antibiotics (e.g. tetracycline, doxycycline): bioavailability may be altered and tetracycline absorption can be reduced by bismuth; separate the doses by a couple of hours

Monitoring

  • Stop and seek advice if symptoms get worse, last more than 2 days, or tinnitus appears
  • Fluid and electrolyte status in patients with diarrhoea, especially frail and elderly patients
  • Caution in patients with blood clotting disorders or gout, or taking medicines for anticoagulation, diabetes or gout

Clinical monograph

How it works

It exerts a local antisecretory, anti-inflammatory and antibacterial action on the gastrointestinal mucosa, with the salicylate moiety contributing antisecretory effects within the gut.

Prescribing in practice

  • Because it releases salicylate, it should be avoided in children and adolescents with viral illness owing to the risk of Reye's syndrome, and used with caution in patients with salicylate hypersensitivity or those taking other salicylates or anticoagulants.
  • It can cause harmless but striking blackening of the tongue and stools, which should not be mistaken for melaena.
  • Avoid prolonged high-dose use because of the potential for bismuth accumulation and salicylate toxicity.

Monitoring

No routine monitoring is required for short-term use; review if symptoms persist or with prolonged or high-dose administration.

Counselling the patient

  • Your stools and tongue may turn black, which is harmless and reversible.
  • Do not give salicylate-containing products to children or teenagers with a feverish illness.
  • Tell your prescriber if you take blood-thinning medicines or other aspirin-like drugs.

Evidence & guidelines

Bismuth subsalicylate has long-established use for gastrointestinal symptom relief and within combination Helicobacter pylori eradication regimens.

Reference: NaTHNaC; NICE CKS; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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