Mesalazine

Mesalazine (BP), 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. Under the Radical Induction Theory of Ulcerative Colitis, 5-ASA is functioning as a free radical trap as well as an anti-inflammatory drug.

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

Formulations

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®).

Dosing depends on the preparation used, in particular, slow-release tablets may have quite different drug delivery characterists 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

Commonly:

  • diarrhoea
  • Nausea
  • Cramping

    • Uncommonly:

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

    • Rarely:

  • Acute pancreatitis,
  • Hepatitis
  • Nephrotic syndrome
  • Blood disorders (including agranulocytosis, aplastic anaemia, leukopaenia, neutropaenia, thrombocytopaenia)

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

  • Allergic lung reactions
  • Allergic myocarditis
  • Methaemoglobinaemia

    • Monitoring

    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.

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