Sulfasalazine and 5-Aminosalicylates (5-ASA)

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.

Examples of these medications include mesalamine, sulfasalazine, and olsalazine. You might recognize them as the brand names Salazopyrin®, 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 do 5-ASAs work?

5-ASAs work locally in the bowel to help control inflammation without suppressing the entire immune system. As such, they allow the damaged gut tissue to heal. 

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Who are 5-ASAs used for?

5-ASAs are 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, that is, applied directly to the mucous membrane (inner lining) of the large intestine, 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.

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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 or maintaining remission 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. Studies have not shown significant therapeutic effects of these medications on people with Crohn's. The grandfather medication, sulfasalazine, may however be effective for treating Crohn's.
  • ​There is also a controversial topic on whether 5-ASAs could help to reduce the risk of colon cancer. The main idea remains that 5-ASAs treat and control ulcerative colitis and by controlling the disease, it could possibly help to prevent cancer risk in the long run.

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Side effects and risks of use

5-ASAs are considered very safe because they do not reach the bloodstream. As such, there are usually no side effects, making them well-tolerated but yet relatively inexpensive medications. Nonetheless, their common side effects include rash, nausea, headaches, increased but rare secretory diarrhea, reduced appetite, or hair loss. 

Sulfapyridine can cause dose-related and hypersensitivity side effects, including allergic reactions to sulfa, reduction in male fertility by temporarily reducing sperm counts (which goes back to normal after stopping the drug), lower absorption of folate in the body (pregnant women are recommended to take folate supplements while on sulfasalazine), and the rare risk of a disease called blood dyscrasia. 

Even rarer "idiosyncratic" 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).

Taking pills could also be a nuisance to people having to keep track of them (a phenomenon known as pill burden) such that they forget to take their medications (compliance becomes an issue).

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Video: 5-ASAs and Inflammatory Bowel Disease

Watch this 6 min video to learn more about 5-ASAs 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.

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

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