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# Mucosal protectants (sucralfate and bismuth)

Drugs that coat or protect the stomach lining instead of lowering acid. Sucralfate seals ulcers; bismuth joins H. pylori regimens.

Updated 2026-11-01

## What they are

Sucralfate and bismuth compounds act locally on the gut lining and are barely absorbed. Sucralfate is used for duodenal ulcer; bismuth subsalicylate treats diarrhoea and upset stomach and is part of bismuth quadruple therapy for Helicobacter pylori.

## Mechanism of action

In acid, sucralfate (an aluminium salt of sulfated sucrose) forms a sticky paste that binds the protein-rich base of an ulcer and shields it from acid, pepsin and bile salts; it also adsorbs pepsin and bile salts and may stimulate local prostaglandins. It does not change acid output. Bismuth coats the mucosa, has antimicrobial effects (including against H. pylori) and reduces intestinal fluid secretion and inflammation; the salicylate in bismuth subsalicylate is absorbed.

Target: Ulcer base and gut mucosa (local action)

## Key points

- Sucralfate needs an acid environment to form its protective paste and does not reduce acid secretion.
- Sucralfate binds other drugs in the gut (fluoroquinolones, digoxin, levothyroxine, phenytoin, warfarin); they are given at least two hours before it.
- Both sucralfate and aluminium antacids add aluminium, which builds up in chronic kidney failure (bone disease, encephalopathy).
- Bismuth turns the tongue and stools black, a harmless change that can be mistaken for melaena.
- Bismuth subsalicylate contains salicylate: risk of Reye syndrome in children and adolescents with viral illness, and of salicylate toxicity with aspirin.

## Drugs in this class

- [**Sucralfate** A sucrose–aluminium complex that sticks to the ulcer base like a bandage and shields it from acid, pepsin and bile. It… Proteins of the ulcer base (local physical barrier)](https://durgical.com/en/pharmacology/sucralfate/)
- [**Bismuth subsalicylate** A bismuth salt for diarrhoea and upset stomach, and part of quadruple therapy for H. pylori. It turns the tongue and… Gut mucosa and microbes (local action)](https://durgical.com/en/pharmacology/bismuth-subsalicylate/)

## Others in the class

- Bismuth subcitrate
- Misoprostol (a prostaglandin that protects the mucosa against NSAIDs)
- Rebamipide

## Test yourself

Think of the answer, then tap the question to see it.

## Why does sucralfate protect an ulcer without changing acid output?

In acid it forms a viscous paste that binds the proteins of the ulcer base and acts as a physical barrier against acid, pepsin and bile.

## Which harmless finding during bismuth treatment can be confused with upper GI bleeding?

Black stools (and a black tongue) caused by bismuth sulfide.

## Why is bismuth subsalicylate avoided in a teenager recovering from influenza or chickenpox?

It contains salicylate, which is linked to Reye syndrome in that setting.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - SUCRALFATE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5ffccd35-5582-4485-8bd6-dbce00343f53) (DailyMed (U.S. National Library of Medicine), 2026); [Medications for the Treatment of Gastric Acidity - Gastroenterology - MSD Manual Professional Edition](https://www.msdmanuals.com/professional/gastrointestinal-disorders/gastritis-and-peptic-ulcer-disease/drug-treatment-of-gastric-acidity) (MSD Manual Professional Edition, 2025); [Bismuth Subsalicylate: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a607040.html) (MedlinePlus (U.S. National Library of Medicine), 2016).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/mucosal-protectants/