Aminosalicylates
Examples
Sulfasalazine (now more commonly used as a DMARD in Rheumatoid Arthritis)
Mesalazine
Indications
Crohn's disease or Ulcerative colitis. These drugs are used in mild - moderate inflammatory bowel disease to treat acute exacerbations and to reduce remission rates.
Contraindications
Contraindications
- Salicylate hypersensitivity
- Sulfasalazine – avoid in children under 2 years old
Caution
- Renal Impairment
- Pregnancy
- Breast Feeding
- G6PD Deficiency
Mechanism
The mechanism of action is unknown, however there are several possible anti-inflammatory actions which may be important at the affected site. Aminosalicylates act as free radical scavengers, inhibit prostaglandin and leukotriene production, and reduce release of IL-1 from cells.
Administration
Oral
PR (enema or suppository)
Mesalazine should be prescribed by brand rather than generically as there can be some characteristic differences between brands.
Adverse Reactions
Common
Rare
- Blood dyscrasias
- Renal dysfunction
- Lupus like syndrome
Interactions
Increased risk of leukopenia if given with immunosuppressants such as azathioprine/mercaptopurine.
Proton pump inhibitors and lactulose have been found to reduce the release of mesalazine as these lower the gastrointestinal pH.
Sulfasalazine decreases the absorption of digoxin and folic acid.
Sulfasalazine can stain some soft contact lenses.
Education
Regular monitoring of renal function is needed. Tell patient to report any unexplained bruising, rashes or infective symptoms as these could indicate a blood abnormality.
Pharmacokinetics
The active molecule in these drugs is 5-aminosalicylate.
In sulfasalazine, 5-aminosalicylate is attached to a sulphonamide group. When this reaches the gut, bacteria cleave it into 5-aminosalicylate and sulphapyridine. It is the systemic absorption of sulphapyridine that causes side effects (like those seen with sulphonamide antibiotics).
Mesalazine is a 5-aminosalicylate in a form that will release that active ingredient in the gut. It has fewer side-effects than sulfasalazine due to the lack of a sulphonamide metabolite.
