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for Inflammatory Bowel Disease (IBD)

5-ASA Medicines


  • There are two members of this group of medicines – sulfasalazine (Salazopyrin) and mesalamine (also known as 5-aminosalicylic acid or 5-ASA).

  • A number of different medicines contain mesalamine with trade (brand) names: Asacol (Apriso), Mezavant (Lialda), Pentasa, Salofalk, Mesalsal, and Dipentum (olsalazine). The main difference between the different brands of mesalamine are the coatings on the pills which affects the way the 5-ASA is delivered to the colon.

  • 5-ASA medicines are primarily used for treatment of:

    • mild-to-moderately active ulcerative colitis.

    • mild-to-moderately active Crohn’s disease affecting the colon. While 5-ASA is used in this situation, there have not been any research evaluations of this approach.

  • 5-ASA medicines (aside from Sulfasalazine) are occasionally used for treatment of:

    • Mild to moderate Crohn’s disease of the small intestine.The evidence for its benefits in this situation is limited.

  • 5-ASA medicines are usually the first treatment used in mild to moderate ulcerative colitis or mild to moderate Crohn’s disease limited to the colon.

  • Combination treatment: It is unknown whether 5-ASA confers added benefit when patients require other therapies such as corticosteroids, immunosuppressants or biologicals.

  • Cost: These medicines are lower in cost than many other medicines for IBD.  There are differences in costs among the various brand name and generic versions. Usually they are covered under provincial and private drug plans.  (See the fact sheet Managing Costs of Medicine for Inflammatory Bowel Disease for more information.)


How do these medicines work?

  • 5-ASA medicines decrease inflammation in the colon, and very little is absorbed into the bloodstream.

  • They do not interfere otherwise with the function of the immune system.

  • They do not influence blood clotting the way ASA (acetylsalicylic acid) or aspirin does.


How well do they work?

  • 1 in 6 patients (17%) receiving 5-ASA pills who have active ulcerative colitis will achieve remission, however another 2 of 6 patients (35%) will achieve a benefit even if not fully in remission.

  • 1 in 4 patients (25%) receiving 5-ASA pills who have ulcerative colitis in remission will remain in remission on continuing the medicine.

  • 1 in 3 patients (33%) receiving 5-ASA enemas in ulcerative colitis limited to the lower part of the colon will achieve remission.

  • 1 in 3 patients (33%) receiving 5-ASA enemas in ulcerative colitis limited to the lower part of the colon in remission will remain in remission on continuing the medicine.

  • If a patient has active ulcerative colitis treated with 5-ASA and the symptoms have not sufficiently improved within 2-3 weeks, a different treatment is often consider.

  • The different forms of oral 5-ASA are considered to be equally effective.

  • The combination of oral and rectal 5-ASA is better at settling active ulcerative colitis than either oral 5-ASA or rectal 5-ASA alone.



How are they taken?


  • Each 5-ASA pill only contain between 400mg and 1200mg (0.4 grams to 1.2 grams) of mesalamine. Recommended daily doses range between 2000mg (2 grams) and 4800mg (4.8 grams) per day.

  • Therefore, you may need to take between 4 and 12 pills per day. It does not matter whether you take them all at once or split up over the day.

  • 5-ASA pills do not have to be taken on an empty stomach or with meals

  • The pills cannot be cut or chewed, this interferes with their effectiveness.The exception to this is Pentasa where the granules can be swallowed.

  • The outer shell of some 5-ASA pills are designed to not be digested, and may be seen in the stool. However, the active medication will still have been absorbed. Sometimes patients pass the 5-ASA pill whole in the stool. If this happens with most of your 5ASA pills then tell your doctor.


Suppositories and Enemeas

  • 5-ASA may be taken as a suppository. Suppositories are used when there is inflammation in the rectum

  • 5-ASA may be taken as an enema. This is a liquid (usually around 100 ml - a little under half a cup) that comes in a tube. The tube is inserted into the anus and the medicine is squeezed into the rectum. The medicine is pushed backward up into the colon by the natural movement of the bowel. It is used to treat inflammation in the lower colon and rectum

  • There is a new enema formulated as a foam rather than a liquid (trade name is Mezera). Persons with active rectal inflammation may find it easier to hold a foam enema than a liquid enema.

Duration of treatment: If the medicine is helpful, it is usually continued for at least a few years, if not indefinitely. 

Stopping 5-ASA: Sometimes patients stop 5-ASA on their own and if they flare they restart on their own. If patients have mild disease the physician and patient may agree to have the patients adjust their own 5ASA doses including restarting if they have stopped on their own.

Side Effects

  • Approximately 30% of sulfasalazine users will experience nausea or abdominal discomfort.

  • Sulfasalazine cannot be taken if you have a sulfa allergy.

  • Mesalamine containing 5-ASAs have a very low likelihood of major side effects. This is because only a very small amount of the active drug is absorbed into the bloodstream.

  • 5-ASA is chemically different than ASA (acetylsalicylic acid or aspirin). Thus, you can take 5-ASA containing pills even if you have been advised by your doctor to avoid taking aspirin.


Sandborn WJ, Feagan BG, Lichtenstein GR (October 2007). "Medical management of mild to moderate Crohn's disease: evidence-based treatment algorithms for induction and maintenance of remission". Alimentary Pharmacology & Therapeutics. 26 (7): 987–1003.

Wang Y, Parker CE, Bhanji T, Feagan BG, MacDonald JK. Oral 5-aminosalicylic acid for induction of remission in ulcerative colitis. Cochrane Database Systematic Review. 2016 Apr 21;4:CD000543

Wang Y, Parker CE, Feagan BG, MacDonald JK. Oral 5-aminosalicylic acid for maintenance of remission in ulcerative colitis. Cochrane Database Systematic  Review. 2016 May 9;(5):CD000544.

Ye B, van Langenberg DR. Mesalazine preparations for the treatment of ulcerative colitis: Are all created equal? 2015 Nov 6;6(4):137-44.

Last reviewed: March 2020

For more information and fact sheets about IBD and its treatment please visit:

Disclaimer: This information is provided for educational purposes only. Always consult a qualified health care professional for your specific care.

Source: This summary provides scientifically accurate information.  It was prepared in a research review by researchers with the IBD Clinical and Research Centre, University of Manitoba with assistance from colleagues in Canada and internationally. 

Acknowledgement: Preparation of this material was supported by funding from the Canadian Institutes of Health Research. 

©2017 Charles N. Bernstein, John R. Walker on behalf of Manitoba IBD Clinical and Research Centre. This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License. You are free to copy and distribute this material in its entirety as long as it is not altered in any way (no derivative works). 

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