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Systematic (IUPAC) name
5-amino-2-hydroxybenzoic acid
CAS number 89-57-6
ATC code A07EC02
PubChem 4075
DrugBank APRD01098
Chemical data
Formula C7H7NO3 
Mol. mass 153.135 g/mol
Pharmacokinetic data
Bioavailability orally: 20-30% absorbed
rectally: 10-35%
Metabolism Rapidly & extensively metabolised intestinal mucosal wall and the liver.
Half life 5 hours after initial dose.
At steady state 7 hours
Excretion  ?
Therapeutic considerations
Pregnancy cat.


Legal status
Routes oral rectal

Mesalazine (INN, BAN), also known as Mesalamine (USAN) or 5-aminosalicylic acid (5-ASA), is an anti-inflammatory drug used to treat inflammation of the digestive tract (Crohn's disease) and mild to moderate ulcerative colitis. Mesalazine is a bowel-specific aminosalicylate drug that is metabolized in the gut and has its predominant actions there, thereby having fewer systemic side effects.

As a derivative of salicylic acid, 5-ASA is also an antioxidant that traps free radicals, which are potentially damaging by-products of metabolism.

5-ASA is considered the active moiety of sulfasalazine, which is metabolized to it.



It is formulated for oral ingestion as tablets or granules, and for rectal administration as rectal suppository, suspension or enemas. It is sold under a variety of brand names (UK: Asacol, Ipocal, Pentasa & Salofalk. US: Canasa, Rowasa, Pentasa, Asacol and Lialda). The newest of these is Lialda, approved by the FDA in January 2007 for induction of remission in ulcerative colitis. Its main benefit is that it needs to be taken only once a day, which provides convenient dosing regimen for patients. Whether convenience leads to improved compliance and adherence to therapy long term remains to be proven. Adherence to IBD therapy is multifactorial.

Dosing depends on the preparation used, in particular, slow-release tablets may have quite different drug delivery characteristics and are not interchangeable.

Preparations that lower stool pH (such as lactulose, a laxative) will affect the binding of Mesalazine in the bowel and will therefore reduce its efficacy.

Side effects


  • Diarrhea
  • Nausea
  • Cramping


  • Headache
  • Exacerbation of the colitis
  • Hypersensitivity reactions (including rash, urticaria, interstitial nephritis and lupus erythematosus-like syndrome)
  • Hair Loss
  • Interstitial nephritis


  • Acute pancreatitis,
  • Hepatitis
  • Nephrotic syndrome
  • Blood disorders (including agranulocytosis, aplastic anaemia, leukopenia, neutropenia, thrombocytopenia)

Mesalazine avoids the sulphonamide side effects of Sulfasalazine (which contains additional (sulfapyridine), but carries additional rare risks of:

  • Allergic lung reactions
  • Allergic myocarditis
  • Methaemoglobinaemia


As a result of the small risks of kidney, liver and blood disorders, blood tests should be taken before and after starting treatment. Patients are advised to report any unexplained bleeding, bruising, purpura, sore throat, fever or malaise that occurs during treatment so that a full blood count can be urgently taken.


This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Mesalazine". A list of authors is available in Wikipedia.
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