Sulfasalazine and 5-Aminosalicylates (5-ASA)

Aminosalicylic acids, or 5-ASAs, limit the production of certain chemicals that trigger inflammation. These medications are generally prescribed to people with mild-to-moderate Crohn’s or colitis. 

What are sulfasalazine and 5-ASAs?

Sulfasalazine is a drug that is made up of two components: sulfapyridine and 5-aminosalicylic acid (5-ASA). This medication has been used since the 1930s to treat inflammation in arthritis and it was later found to do the same in ulcerative colitis.

At first, scientists did not know why sulfasalazine was effective in treating colitis but studies have then showed that it was due to the 5-ASA component of the drug. Later, medications for colitis started to exclude the sulfapyridine component of the drug because it was found to be responsible for the side effects. These newly-designed drugs with fewer side effects would go on to be called 5-ASAs.

Aminosalicylic acids, or 5-ASAs for short, are therefore known as grandfather medications in the treatment of colitis. These drugs act as anti-inflammatory agents to reduce the severity of bowel symptoms in mild-to-moderate ulcerative colitis.

5-ASAs have been reported to be generally more useful for colitis than Crohn's disease. Therefore, it remains uncertain how effective they are at treating Crohn's. They are considered to be topical (i.e. applied directly to the mucous membrane of the large intestine in this case) because they coat the colon. This is why they are more useful for colitis, which is known to affect the inner lining of the colon, rather than Crohn's. As such, 5-ASAs are considered to be first-line medications in the treatment of colitis.

Examples of these medications include mesalamine, sulfasalazine, and olsalazine. You might recognize them as the brand names Asacol®, Mezavant®, Pentasa®, Salofalk®, and Teva®

In addition to oral pills, these medications come in the form of suppositories, rectal foams, and liquid enemas. 

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How effective are sulfasalazine and 5-ASAs?

Here is a summary of the effectiveness of sulfasalazine/5-ASAs for management of IBD:

  • 5-ASAs are very effective at inducing remission in active mild-to-moderate ulcerative colitis.

  • 5-ASAs are very effective at preventing relapse in inactive ulcerative colitis.

  • 5-ASAs are NOT effective at inducing remission in active Crohn's disease or preventing relapse in inactive Crohn's disease.

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Side effects and risks of use

5-ASAs are considered very safe because they do not reach the bloodstream. Common side effects include rash, nausea, headaches, increased diarrhea, reduced appetite, or hair loss. 

Sulfapyridine can cause dose-related and hypersensitivity side effects, including reduction in male fertility (which goes back to normal after stopping the drug) and the rare risk of a disease called blood dyscrasia. 

Rare side effects of the mesalamine component of these drugs include interstitial nephritis (a kidney disorder), pancreatitis (inflammation of the pancreas), pneumonitis (lung inflammation), pericarditis (inflammation of a tissue surrounding the heart), and hepatitis (liver inflammation).

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Video: 5-ASAs and Inflammatory Bowel Disease

Watch this video to learn more about 5-ASAs (6 min) used in the treatment of Crohn's disease and ulcerative colitis, including how these medications work in IBD, what they are used for, which types of patients can access 5-ASAs, potential benefits, side effects, and risks.


Dr. John K. Marshall (MD, MSc, FRCPC, CAGF, AGAF), Professor of Medicine, Director, Division of Gastroenterology, McMaster University.

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