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Gastroprotective

Mesalazine (5-Aminosalicylic Acid)

Brand names: Asacol, Mezavant, Octasa, Pentasa

Used in: Inflammatory Bowel Disease

Mesalazine (5-aminosalicylic acid) is used to induce and maintain remission in ulcerative colitis and in some Crohn's disease.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It acts topically on the bowel mucosa with local anti-inflammatory effects; different formulations deliver it to different parts of the gut.

Prescribing in practice

  • Formulations release at different sites and are not interchangeable — prescribe by brand.
  • Rare but important renal toxicity (interstitial nephritis) and blood dyscrasias can occur.
  • It is generally far better tolerated than sulfasalazine (no sulfapyridine component).

Monitoring

Check renal function before starting and periodically; review the blood count if features of a dyscrasia occur.

Counselling the patient

  • Stay on the same brand.
  • Report unexplained bleeding, bruising, sore throat, or a marked change in urine output.
  • Take it regularly to maintain remission, even when you feel well.

Evidence & guidelines

First-line for inducing and maintaining remission in ulcerative colitis (NICE NG130).

Reference: BSG UC Guidelines 2019; NICE NG130 IBD; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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