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[Pharmacology](https://durgical.com/en/pharmacology/) · [Aminosalicylates (5-ASA)](https://durgical.com/en/pharmacology/classes/aminosalicylates/)

# Mesalazine

5-aminosalicylic acid packaged to reach the inflamed bowel. It calms the lining locally and is a base treatment for ulcerative colitis.

Updated 2026-11-01

- Class: [Aminosalicylates (5-ASA)](https://durgical.com/en/pharmacology/classes/aminosalicylates/)
- Target: Colonic mucosa (local anti-inflammatory action)
- ATC code: A07EC02

Also called: Mesalamine, 5-aminosalicylic acid, 5-ASA

## Mechanism of action

Mesalazine acts on the bowel lining from the lumen. It is thought to reduce mucosal prostaglandins and leukotrienes (cyclooxygenase and lipoxygenase pathways), to interfere with inflammatory cytokines through NF-κB and to scavenge reactive oxygen species. Unformulated 5-ASA would be absorbed early in the small bowel, so tablets, granules, enemas and suppositories release it by pH or time where the disease is.

- pH- or time-dependent release delivers 5-ASA to ileum and colon
- Acts topically on the inflamed mucosa
- Lowers prostaglandins, leukotrienes and cytokine signalling

## Pharmacokinetics

**Absorption**
Only part is absorbed; most stays in the bowel lumen

**Metabolism**
Acetylated in the gut wall and liver to N-acetyl-5-ASA

**Elimination**
Absorbed drug in urine as N-acetyl-5-ASA; the rest in stool

## Indications

- Induction of remission in mild to moderate ulcerative colitis [Ulcerative colitis →](https://durgical.com/en/conditions/ulcerative-colitis/)
- Maintenance of remission in ulcerative colitis (oral and rectal forms) [Ulcerative colitis →](https://durgical.com/en/conditions/ulcerative-colitis/)
- Some cases of Crohn's disease affecting the colon or ileum [Crohn disease →](https://durgical.com/en/conditions/crohn-disease/)

## Adverse effects

### Common

- Headache
- Nausea
- Abdominal pain
- Nasopharyngitis
- Photosensitivity

### Serious (rare, important)

- Acute intolerance syndrome that mimics a flare of colitis (cramps, bloody diarrhoea, fever)
- Kidney injury: interstitial nephritis, minimal change disease and, rarely, kidney failure
- Hypersensitivity, including myocarditis and pericarditis
- Severe skin reactions (SJS/TEN, DRESS)
- Liver failure; kidney stones made of mesalazine
- Blood dyscrasias, especially in older adults

## Contraindications

- Hypersensitivity to salicylates or aminosalicylates

## Key interactions

**Nephrotoxic drugs, including NSAIDs**
Higher risk of kidney injury; kidney function is watched

**Azathioprine or mercaptopurine**
Higher risk of blood disorders; blood counts are checked

**Urinary normetanephrine tests (liquid chromatography)**
Falsely high results

## What is monitored

- Kidney function (creatinine, urinalysis) before starting and periodically
- Complete blood count, especially in older adults or with thiopurines
- Symptoms of colitis that worsen soon after starting (intolerance syndrome)
- Liver tests in known liver disease

## Administration and safety

- Delayed-release tablets are swallowed whole, not cut, crushed or chewed.
- Different brands and forms release the drug in different parts of the gut and are not interchanged without a prescriber's decision.
- Rectal forms (enemas, suppositories, foam) treat distal colitis and proctitis.
- Good fluid intake lowers the risk of kidney stones.

## Nursing care

- Check baseline creatinine and urinalysis before the first dose.
- Report worsening cramps, bloody diarrhoea or fever soon after starting: they may be intolerance, not a flare.
- Teach to report rash, chest pain or shortness of breath (possible myocarditis or pericarditis).
- Advise sun protection and good hydration.
- Teach that tablet shells seen repeatedly in the stool are reported.

## Pregnancy and breastfeeding

Patients already on mesalazine usually continue it in pregnancy; there is no clear evidence of harm to the baby. Small amounts reach breast milk, and diarrhoea in the baby has rarely been reported.

## Memory aid

Mesalazine = «MEssage to the mucosa»: 5-ASA delivered where the colitis is.

## Test yourself

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

## Why is mesalazine given in special delayed-release forms?

Plain 5-ASA would be absorbed in the upper small bowel; the formulations release it in the ileum and colon, where it acts topically.

## Which mesalazine adverse effect can be confused with a flare of ulcerative colitis?

The acute intolerance syndrome, with cramps, bloody diarrhoea and fever.

## Which laboratory test is checked before and during mesalazine treatment?

Kidney function, because of the risk of interstitial nephritis.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/mesalazine/)

## Related drugs

- [Sulfasalazine](https://durgical.com/en/pharmacology/sulfasalazine/)
- [Azathioprine](https://durgical.com/en/pharmacology/azathioprine/)
- [Prednisolone](https://durgical.com/en/pharmacology/prednisolone/)

## Related conditions

- [Ulcerative colitis](https://durgical.com/en/conditions/ulcerative-colitis/)
- [Crohn disease](https://durgical.com/en/conditions/crohn-disease/)

[← Back to the class: Aminosalicylates (5-ASA)](https://durgical.com/en/pharmacology/classes/aminosalicylates/)

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 - MESALAMINE tablet, delayed release](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=00f77203-3615-47e8-ae25-6e1cf8a2a00a) (DailyMed (U.S. National Library of Medicine), 2026); [Mesalazine: a medicine to treat inflammatory bowel conditions including ulcerative colitis and Crohn's disease - NHS](https://www.nhs.uk/medicines/mesalazine/) (NHS (National Health Service, UK), 2025); [Mesalamine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a688021.html) (MedlinePlus (U.S. National Library of Medicine), 2024); Farmacología básica y clínica (Katzung), 16.ª ed., cap. 62 (McGraw Hill, 2025).

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Source: https://durgical.com/en/pharmacology/mesalazine/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/mesalazine/