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Generic name: mesalamine
Dosage form: rectal suppository
Drug class: 5-aminosalicylates

Medically reviewed by Philip Thornton, DipPharm. Last updated on Apr 4, 2023.

What is Canasa?

Canasa (mesalamine) is a suppository used to treat a type of inflammatory bowel disease called ulcerative proctitis. Ulcerative proctitis causes inflammation, redness and ulcers to develop in the lining of the rectum, which is at the end of your large intestine. Ulcerative proctitis may also affect nearby parts of the colon.

Canasa contains the medication mesalamine, which is also known as mesalazine or 5-aminosalicylic acid (5-ASA). It is contained inside a base of hard fat. Canasa is used topically and is inserted into the rectum. As the warmth of your body melts the hard fat base, the drug is released into the area where it needs to work.

Canasa belongs to a class of drugs called aminosalicylates. Canasa is thought to work by reducing inflammation in the epithelial cells that line the colon. Its anti-inflammatory action may result from its ability to block the enzyme cyclooxygenase (COX) and inhibit prostaglandin production in the colon. COX and prostaglandins (a group of lipids) are both involved in generating an inflammatory response.

Medications containing mesalamine have been available for many years, however, Canasa was first approved by the US Food and Drug Administration (FDA) in 2001.

When Canasa was first approved it was available as a 500 mg strength suppository that needed to be used twice a day. This has been replaced by a 1000 mg strength suppository that only needs to be used at night. Generic versions of Canasa are also available.

What is Canasa used for?

Canasa is a prescription medicine used to treat adults with active ulcerative proctitis (ulcerative rectal colitis).

It is not known if Canasa is safe and effective in children.

Important information

Canasa is for rectal use only. Do not take Canasa by mouth.

Who should not use Canasa?

Do not use Canasa if your are:

  • allergic to medicines that contain salicylates, including aspirin.
  • allergic to mesalamine or any of the ingredients in Canasa. See below for a complete list of ingredients in Canasa.

Ask your doctor if you are not sure if your medicine is listed above.

What should I tell my doctor before using Canasa?

Before using Canasa, tell your doctor if you have any medical conditions, including if you:

  • have a history of allergic reaction to the medicine sulfasalazine (Azulfidine).
  • have kidney problems.
  • have ever had inflammation of the sac around your heart (pericarditis).
  • have liver problems.

How should I use Canasa?

  • Use Canasa exactly as prescribed by your doctor. Your doctor will tell you how long to continue using Canasa.
  • Canasa comes as a suppository that you insert into your rectum.
  • Do not cut or break the suppository.
  • Use Canasa 1 time each day at bedtime, for 3 to 6 weeks. It is not known if Canasa is safe and effective for use for longer than 6 weeks.
  • After you insert Canasa in your rectum, try to keep (retain) the suppository in your rectum for 1 to 3 hours or longer if possible.
  • It is important for you to stay well hydrated during treatment with Canasa. Be sure to drink plenty of fluids while taking Canasa.

What happens if I miss a dose?

If you miss a dose of Canasa, insert it as soon as you remember. If it is almost time for your next dose, skip the missed dose. Insert the next dose at your regular time. Do not insert 2 doses at the same time.

What should I avoid while using Canasa?

Canasa can stain surfaces including clothing and other fabrics, flooring, painted surfaces, marble, granite, vinyl and enamel. Keep Canasa away from these surfaces to prevent staining.

If you have atopic dermatitis or eczema you may become more sensitive to the sun while using Canasa. Avoid sun exposure, wear protective clothing, and use a broad-spectrum sunscreen when outdoors.

Dosing information

The recommended dose of Canasa for adults is 1000 mg administered rectally once daily at bedtime for 3 to 6 weeks. Safety and effectiveness beyond 6 weeks have not been established.

See full prescribing information for more information about Canasa dosing.

What are the side effects of Canasa?

Canasa may cause serious side effects, including:

  • kidney problems. Your doctor will do certain tests before you start using Canasa and during your treatment with Canasa.
  • acute intolerance syndrome and other allergic reactions. Some people who use Canasa can have allergic type reactions, including Acute Intolerance Syndrome. Other allergic reactions can cause heart problems including an inflammation of the sac around the heart (pericarditis), blood problems, and problems with other organs in the body including the kidneys, liver and lungs. These problems usually happen in people who have had an allergic reaction to medicines containing sulfasalazine. Stop using Canasa and tell your doctor right away if you get any of these symptoms:
    • cramps
    • fever
    • stomach (abdominal) pain
    • headache
    • bloody diarrhea
    • rash
    • chest pain
    • shortness of breath
    • decrease in the amount of urine
    • fatigue
    • eye inflammation
  • liver problems. This can happen in people who have a history of liver problems and have taken other medicines that contain mesalamine. Tell your doctor right away if you get any of these symptoms while using Canasa:
    • yellowing of your eyes
    • flu-like symptoms
    • itchy skin
    • nausea or vomiting
    • feeling very tired
  • serious skin reactions. Some people who use Canasa can have severe skin reactions. Stop using Canasa and tell your doctor right away if you develop any of the following signs or symptoms of a severe skin reaction, including:
    • blisters or peeling of your skin
    • mouth sores
    • blisters on your lips, or around your mouth or eyes
    • high fever or flu-like symptoms
    • enlarged lymph nodes
    • skin rash
  • sun sensitivity. Canasa can make your skin sensitive to the sun if you have skin conditions such as atopic dermatitis and atopic eczema. Try to limit your time in the sun. You should use sunscreen and wear a hat and clothes that cover your skin if you have to be in the sunlight.
  • kidney stones. Drink plenty of fluids when using Canasa to decrease your chance of getting kidney stones. Call your doctor right away if you get any of these symptoms:
    • severe pain in your side
    • severe pain in your back
    • blood in your urine

The most common side effects of Canasa include:

  • dizziness
  • rectal pain
  • acne
  • fever
  • inflammation of the large intestine (colitis)
  • rash

These are not all of the possible side effects of Canasa.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins and herbal supplements.

Using Canasa with certain other medicines may affect each other. Using Canasa with other medicines can cause serious side effects.

Especially tell your doctor if you take nonsteroidal anti-inflammatory drugs (NSAIDS), or medicines that contain azathioprine or 6-mercaptopurine. Taking Canasa with NSAIDS may cause kidney problems. Taking Canasa with azathioprine or 6-mercaptopurine may cause blood problems. Ask your doctor if you are not sure if you are taking one of these medicines.

Your doctor may do certain tests during treatment with Canasa.

Know the medicines you take. Keep a list of them to show your doctor and pharmacist when you get a new medicine.

Pregnancy and breastfeeding

Tell your doctor if you are pregnant or plan to become pregnant. It is not known if Canasa can harm your unborn baby.

Tell your doctor if you are breastfeeding or plan to breastfeed. Canasa can pass into your breast milk. Talk to your doctor about the best way to feed your baby if you use Canasa.


  • Store Canasa at room temperature between 68°F to 77°F (20°C to 25°C).
  • Canasa may be refrigerated.
  • Keep Canasa away from direct heat, light, or humidity.

Keep Canasa and all medicines out of the reach of children.

What are the ingredients in Canasa?

Active ingredients: mesalamine

Inactive ingredients: hard fat base

Canasa is distributed by Allergan USA, Inc. Madison, NJ 07940.

Popular FAQ

Research studies looking at patients who received daily oral doses of 4 to 6 grams of mesalamine showed that 80% of patients achieved complete or significant clinical improvement within 4 weeks.

Mesalamine is an antiinflammatory, not an immunosuppressant. It may be one of the first treatments used for ulcerative colitis (UC) to lessen symptoms like diarrhea, rectal bleeding, or stomach pain. Immunosuppression is not a listed side effect for mesalamine. Other medicines used for UC, like prednisone, can suppress the immune system.

The best time to take or use mesalamine will depend on the specific product you are using and why you are using it (ulcerative colitis induction or maintenance, ulcerative proctitis). Some products may need to be taken with food while others are taken on an empty stomach. Check with your doctor.

Some forms of mesalamine are used long-term as a maintenance therapy in ulcerative colitis to help prevent symptoms from flaring up. Not all forms or brands of mesalamine are used long-term, so check with your doctor about your specific medicine. Call your doctor if your ulcerative colitis symptoms get worse after starting treatment.

Brand name products of mesalamine may be more expensive than generic options. Some, but not all mesalamine products are available as generics. Your insurance should help pay for generics, or if you are paying out-of-pocket, ask your healthcare provider if there is a more affordable option.

Mesalamine is available as delayed-release tablets or capsules, extended-release capsules, and rectal preparations like suppositories or enemas. The maximum dose will depend upon the specific product you are using and your diagnosis. Only use the dose prescribed by your doctor.

Mesalamine is used in some patients with ulcerative colitis as a maintenance (long-term) treatment to help you stay in remission (without active symptoms). Other treatments for ulcerative colitis or proctitis are only taken short-term. Ask your doctor when you can stop taking treatment.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.