Canasa (mesalamine) is a brand-name prescription medication. It’s approved by the Food and Drug Administration (FDA) to treat mild to moderate symptoms of ulcerative proctitis in adults.

Ulcerative proctitis is a condition that causes swelling and sores in your rectum. It can cause symptoms such as blood in your stool, abdominal pain, or diarrhea.

Drug details

Canasa contains the active drug mesalamine and belongs to a class of drugs called aminosalicylates.

Canasa comes as a suppository that’s inserted rectally. It comes in one strength: 1000 milligrams (mg).

Canasa is only approved for use in adults. At this time, it’s not known if Canasa is safe or effective in children.

Effectiveness

For information about the effectiveness of Canasa, see the “Canasa uses” section below.

Canasa is a brand-name drug that contains the active drug mesalamine. This active drug is also available as a generic medication. A generic drug is an exact copy of the active drug in a brand-name medication.

The generic is considered to be as safe and effective as the original drug. Generics tend to cost less than brand-name drugs.

If you’re interested in taking the generic form of Canasa, talk with your doctor. They can tell you if it comes in forms and strengths that can be used for your condition.

Canasa can cause mild or serious side effects. The following lists contain some of the key side effects that may occur while taking Canasa. These lists do not include all possible side effects.

For more information about the possible side effects of Canasa, talk with your doctor or pharmacist. They can give you tips on managing any side effects that may be concerning or bothersome.

Note: The Food and Drug Administration (FDA) tracks side effects of drugs it has approved. If you would like to notify the FDA about a side effect you’ve had with Canasa, you can do so through MedWatch.

Mild side effects

Mild side effects* of Canasa can include:

Most of these side effects may go away within a few days or a couple of weeks. However, if they become more severe or don’t go away, talk with your doctor or pharmacist.

* This is a partial list of mild side effects from Canasa. To learn about other mild side effects, talk with your doctor or pharmacist, or view Canasa’s prescribing information.

Serious side effects

Serious side effects from Canasa aren’t common, but they can occur. Call your doctor right away if you have serious side effects. Call 911 or your local emergency number if your symptoms feel life threatening or you think you’re having a medical emergency.

Serious side effects and their symptoms can include:

  • Kidney problems. Symptoms can include:
    • swelling of your legs or arms
  • Sensitivity to the sun. Symptoms can include:
    • itching or burning in skin exposed to the sun
    • skin that burns easier than usual
    • blistering of the skin
  • Severe skin reaction. Symptoms can include:
    • redness or deepening of skin color
    • peeling of the skin
    • fever
  • Acute intolerance syndrome.*
  • Kidney stones.*
  • Black stool.*
  • Allergic reaction.*

* For more information about this side effect, see “Side effect details” below.

Side effect details

Here’s some detail on certain side effects this drug may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Canasa.

Discolored stool, such as black stool

You may experience discolored stool while taking Canasa. However, this side effect was not reported in clinical trials. Instead, discolored stool, such as black stool, was reported in postmarketing studies of this medication. Postmarketing studies collect information about a drug after it has been approved by the FDA.

In some cases, black stool can indicate bleeding in your digestive tract, which can be dangerous. So, it’s important that you talk with your doctor if you are experiencing black stool. They will help you determine what may be causing the black stool.

Although discolored stool was not a reported side effect of Canasa, it may occur. If you experience discolored stool, such as black stool, be sure to tell your doctor. To find out how often this side effect occurred in clinical trials, see the drug’s prescribing information.

Acute intolerance syndrome

You may develop a condition called acute intolerance syndrome from taking Canasa. With this condition, your body is unable to tolerate Canasa. Although this is not a common side effect of taking Canasa, it may occur. If you develop acute intolerance syndrome, you may experience symptoms similar to an allergic reaction or worsening of your condition. Symptoms may include:

If you experience these symptoms while taking Canasa, talk with your doctor. They can help determine if Canasa is the cause of your symptoms. If you experience acute intolerance syndrome, your doctor will recommend stopping Canasa treatment. Your symptoms of acute intolerance syndrome will likely ease after you stop taking the drug.

If you experience symptoms that may be related to acute intolerance syndrome, be sure to talk with your doctor. To find out how often this side effect occurred in clinical trials, see the drug’s prescribing information.

Kidney stones

It’s possible to develop kidney stones while taking Canasa. However, kidney stones were not one of the most common side effects reported in clinical trials. Kidney stones are hard masses that begin in your kidneys.

Symptoms may include:

  • nausea or vomiting
  • fever
  • pain in your side or back
  • blood in your urine

You can also prevent kidney stones from recurring by drinking lots of fluids while you’re taking Canasa. This can decrease your risk of kidney stones occurring during your treatment.

If you develop any symptoms of kidney stones, it’s important to talk with your doctor right away. They can help determine if you may need treatment for your kidney stones. To find out how often this side effect occurred in clinical trials, see the drug’s prescribing information.

Allergic reaction

As with most drugs, some people can have an allergic reaction after taking Canasa.

Symptoms of a mild allergic reaction can include:

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include:

  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your tongue, mouth, or throat
  • trouble breathing

Call your doctor right away if you have an allergic reaction to Canasa, as the reaction could become severe. Call 911 or your local emergency number if your symptoms feel life threatening or if you think you’re having a medical emergency.

The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to fit your needs.

Drug forms and strengths

Canasa comes as a suppository that’s inserted rectally. It comes in one strength: 1000 milligrams (mg).

Dosage for ulcerative proctitis

The usual dosage of Canasa for ulcerative proctitis is 1000 mg inserted rectally once per day at bedtime. Your doctor will likely recommend that you only use Canasa for 3 to 6 weeks to treat your condition.

What if I miss a dose?

If you miss a dose of Canasa, take it as soon as you remember. However, if it’s almost time for your next dose, skip your missed dose and take your next dose of Canasa on your normal schedule. Do not take two doses of Canasa at once to make up for a missed dose.

If you missed your dose of Canasa and you’re unsure when to take your next dose, talk with your doctor or pharmacist.

To help make sure that you don’t miss a dose, try using a medication reminder. This can include setting an alarm or using a timer. You could also download a reminder app on your phone.

Will I need to use this drug long term?

In most cases, you will only take Canasa for 3 to 6 weeks. It’s not known if Canasa is safe or effective to use after 6 weeks. Talk with your doctor about the best treatment plan for you and how long you should take Canasa.

As with all medications, the cost of Canasa can vary. To find current prices for Canasa suppositories in your area, check out GoodRx.com.


The cost you find on GoodRx.com is what you may pay without insurance. The actual price you’ll pay depends on your insurance plan, your location, and the pharmacy you use.

Before approving coverage for Canasa, your insurance company may require you to get prior authorization. This means your doctor and insurance company will need to communicate about your prescription before the insurance company will cover the drug. The insurance company will review the prior authorization request and decide if the drug will be covered.

If you’re not sure whether you’ll need to get prior authorization for Canasa, contact your insurance company.

Financial and insurance assistance

If you need financial support to pay for Canasa, or if you need help understanding your insurance coverage, help is available.

Allergan, the manufacturer of Canasa, offers a Canasa Savings Card. For more information and to find out if you’re eligible for support, call 844-800-9881 or visit the program website.

To learn more about saving money on prescriptions, check out this article.

Mail-order pharmacies

Canasa may be available through a mail-order pharmacy. Using this service may help lower the drug’s cost and allow you to get your medication without leaving home.

If you don’t have insurance, you can ask your doctor or pharmacist about online pharmacy options.

Generic version

Canasa is available in a generic form called mesalamine. A generic drug is an exact copy of the active drug in a brand-name medication. The generic is considered to be as safe and effective as the original drug. And generics tend to cost less than brand-name drugs. To find out how the cost of mesalamine compares with the cost of Canasa, visit GoodRx.com.

If your doctor prescribed Canasa, but you’re interested in taking mesalamine instead, talk with your doctor. They may recommend one version or the other. You’ll also need to check your insurance plan, as it may only cover one version.

Other drugs are available that can treat ulcerative proctitis. Some may be a better fit for you than others. If you’re interested in finding an alternative to Canasa, talk with your doctor. They can tell you about other medications that may work well for you.

Note: Some of the drugs listed here are used off-label to treat these specific conditions. Off-label drug use is when a drug that’s approved by the Food and Drug Administration (FDA) is used for a purpose other than what it’s approved for.

Alternatives for ulcerative proctitis

Examples of other drugs that may be used to treat ulcerative proctitis include:

Here are answers to some frequently asked questions about Canasa.

Is Canasa used for ulcerative colitis?

At this time, Canasa is only approved to treat ulcerative proctitis. This is a condition that causes swelling or sores in your rectum.

Ulcerative colitis (UC) is similar to ulcerative proctitis. UC causes swelling or sores to occur throughout the large intestine. Since UC affects more area, it may cause more symptoms to occur.

Canasa works in the rectum to treat symptoms of ulcerative proctitis. Since UC may affect other areas of the colon, Canasa may not work as well to treat the symptoms of UC. However, it’s possible for your doctor to prescribe Canasa off-label to treat your symptoms of UC. Off-label drug use is when a drug that’s approved by the Food and Drug Administration is prescribed for a purpose other than what it’s approved for.

In addition, there are other forms of mesalamine (the active drug in Canasa) that are approved to treat UC. For example, mesalamine comes as a delayed-release capsule, such as Delzicol. It also comes as an enema, such as Rowasa.

If you have UC, talk with your doctor about the best treatment plan for you.

Is Canasa the same as mesalamine?

Canasa contains the active drug mesalamine. So, Canasa is a mesalamine suppository. A suppository is inserted rectally to treat your symptoms of ulcerative proctitis in the area where they occur.

However, mesalamine also comes in other forms and may be used to treat other conditions. For example, mesalamine comes as:

Talk with your doctor to determine which form of mesalamine is best to treat your condition.

Can older adults use Canasa?

Yes, older adults can take Canasa. However, it’s possible for people older than age 65 years to be at an increased risk of side effects from Canasa.

Specifically, older adults may be at an increased risk of developing blood disorders, kidney problems, liver problems, or heart problems during treatment. However, clinical trials of Canasa didn’t include enough older adults to see if these side effects may occur more frequently.

Due to this possible risk, if you are older than age 65 years, your doctor may monitor you more often throughout treatment with Canasa. They may recommend that you have your blood levels checked to be sure that Canasa isn’t causing some of these side effects.

If you are an older adult and are interested in using Canasa, talk with your doctor. They can help you determine if the drug is a safe treatment option for you.

The Food and Drug Administration (FDA) approves prescription drugs such as Canasa to treat certain conditions. Canasa may also be used off-label for other conditions. Off-label drug use is when an FDA-approved drug is prescribed for a purpose other than what it’s approved for.

Canasa for ulcerative proctitis

Canasa is approved by the FDA to treat mild to moderate ulcerative proctitis in adults. Ulcerative proctitis is a condition that causes swelling or sores to occur in the rectum. Symptoms of ulcerative proctitis may include:

  • blood or mucus in your stool
  • stomach pain
  • diarrhea
  • having to use the bathroom more often than usual

At this time, Canasa is not approved to treat ulcerative colitis. However, for more information about Canasa for ulcerative colitis, see the “Common questions about Canasa” section above.

To learn more about ulcerative proctitis or ulcerative colitis, visit our MNT hub for inflammatory bowel disease (IBD).

Effectiveness for ulcerative proctitis

Canasa has been found to be an effective treatment option for people with ulcerative proctitis. In fact, the American Gastroenterological Association recommends suppositories with mesalamine (the active drug in Canasa) as a treatment option for people with ulcerative proctitis.

For more information on how Canasa performed in clinical trials, see the drug’s prescribing information. If you have any additional questions about whether Canasa may be an effective treatment option for you, talk with your doctor.

There are no known drug interactions between Canasa and alcohol. However, some of the side effects of Canasa may become worse if you are also drinking alcohol during your treatment. For example, you may be at an increased risk of side effects such as dizziness if you consume alcohol during treatment with Canasa.

Talk with your doctor about how much alcohol, if any, is safe for you to drink while you take Canasa.

Canasa can interact with several other medications. It’s also possible for Canasa to interact with certain supplements and foods, but no interactions have been reported in clinical trials.

Different interactions can cause different effects. For instance, some interactions can interfere with how well a drug works. Other interactions can increase side effects or make them more severe.

Canasa and other medications

Below is a list of medications that can interact with Canasa. This list does not contain all drugs that may interact with Canasa.

Before taking Canasa, talk with your doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you use. Sharing this information can help you avoid potential interactions.

If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Types of drugs that can interact with Canasa include:

  • Nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs are medications that can be used for pain, swelling, or fever. Taking Canasa in combination with NSAIDs may increase your risk of kidney problems. Examples of NSAIDs include:
  • Nephrotoxic drugs. Nephrotoxic medications may be used for many different conditions, such as infections, mood disorders, or transplants. Taking nephrotoxic drugs in combination with Canasa can increase your risk of kidney problems. Examples of nephrotoxic drugs include:
    • vancomycin (Vancocin)
    • tacrolimus (Prograf)
  • Azathioprine or 6-mercaptopurine. These drugs may be used to treat ulcerative proctitis. They may increase your risk of side effects, such as blood disorders or problems with bone marrow.

Canasa and herbs and supplements

There aren’t any herbs or supplements that have been specifically reported to interact with Canasa. However, you should still check with your doctor or pharmacist before using any of these products while taking Canasa.

Canasa and foods

There aren’t any foods that have been specifically reported to interact with Canasa. If you have any questions about eating certain foods with Canasa, talk with your doctor.

Canasa and lab tests

If you need to have a normetanephrine test done using urine, taking Canasa may affect your test results. Normetanephrine urine tests may be used to diagnose tumors on your adrenal gland. If you need to have this test done, tell your doctor that you are taking Canasa. Your doctor can recommend other types of normetanephrine tests that will not interact with Canasa.

You should take Canasa according to the instructions your doctor gives you.

Canasa comes as a suppository that’s inserted rectally.

It’s also important to note that this medication can stain clothing, fabrics, and certain other materials such as floors, granite, and painted surfaces. Keep this medication away from these materials to prevent staining.

When to take

Typically, you’ll take your dose of Canasa once per day at bedtime. After you insert your dose of Canasa, the manufacturer recommends retaining the dose for 1 to 3 hours if you can. You should use this medication for 3 to 6 weeks.

For step-by-step instructions on how to use Canasa, see the instructions for use.

To help make sure you don’t miss a dose, try using a medication reminder. This can include setting an alarm or using a timer. You could also download a reminder app on your phone.

Accessible labels and containers

If your prescription label is hard to read, talk with your doctor or pharmacist. Some pharmacies offer labels that have large print, braille, or a code you scan with a smartphone to convert text to speech. If your local pharmacy doesn’t have these options, your doctor or pharmacist may be able to direct you to one that does.

Taking Canasa with food

Canasa is a suppository medication that’s inserted rectally. It’s not affected by food. So, you can take your dose of Canasa with or without food. However, be sure to drink a lot of fluids during your treatment.

Can Canasa be crushed, split, or chewed?

Canasa suppositories should not be crushed, split, or chewed. When you take your dose of Canasa, be sure to insert the whole suppository.

Canasa is prescribed to treat ulcerative proctitis in adults. This is a condition that causes swelling and sores in your rectum.

It’s not known exactly how Canasa works to treat ulcerative proctitis. However, it’s believed to work in the rectum to decrease the swelling and inflammation that occurs in people with the condition.

For more information about Canasa for ulcerative proctitis, see “Canasa uses” above.

How long does it take to work?

Canasa will begin working to decrease inflammation right after you take your first dose of medication. You may notice a decrease in your symptoms soon after starting treatment with Canasa.

It’s not known if Canasa is safe to take during pregnancy. Animal studies didn’t show harm during pregnancy. However, animal studies do not always predict what may happen in humans.

If you are pregnant or plan to become pregnant, talk with your doctor before taking Canasa. They can help determine if Canasa is a safe treatment option for you.

It’s unknown if Canasa is safe to take during pregnancy. If you’re sexually active and you or your partner can become pregnant, talk with your doctor about your birth control needs while you’re taking Canasa.

For more information about Canasa treatment during pregnancy, see the “Canasa and pregnancy” section above.

Canasa may pass into breast milk. Some children breastfed by people taking Canasa may experience side effects, such as diarrhea.

If you are breastfeeding or planning to, talk with your doctor about the safest way to feed your child while you’re taking Canasa.

This drug comes with several precautions. Before taking Canasa, talk with your doctor about your health history. Canasa may not be right for you if you have certain medical conditions or other factors affecting your health. These include:

  • Kidney problems. Canasa may cause kidney problems and worsen existing kidney problems. Tell your doctor about any kidney problems you have before starting Canasa. They may recommend monitoring of your kidneys throughout your treatment with Canasa. In some cases, if you have severe kidney problems, your doctor may recommend a different treatment option for you.
  • Heart problems. Canasa can cause heart problems or worsen existing heart problems. If you have a history of heart inflammation, such as pericarditis, talk with your doctor before starting Canasa. They can advise if Canasa is safe for you.
  • Liver problems. Canasa may increase your risk of liver failure. If you have a history of liver problems, talk with your doctor before starting Canasa. In some cases, your doctor may recommend monitoring your liver function with blood tests during your treatment. If you have severe liver problems, your doctor may recommend a different treatment option for you.
  • Allergic reaction. If you’ve had an allergic reaction to Canasa or any of the ingredients in Canasa, your doctor will likely not prescribe Canasa. Ask your doctor what other medications are better options for you.
  • Pregnancy. It’s unknown if Canasa is safe to take during pregnancy. To learn more, see the “Canasa and pregnancy” section above.
  • Breastfeeding. Canasa may pass into breast milk. For more information, see the “Canasa and breastfeeding” section above.

Note: For more information about the potential negative effects of Canasa, see the “Canasa side effects” section above.

Taking more than the recommended dosage of Canasa can lead to serious side effects.

Do not take more Canasa than your doctor recommends.

Overdose symptoms

Symptoms of an overdose can include:

What to do in case of overdose

If you think you’ve taken too much of this drug, call your doctor. You can also call the American Association of Poison Control Centers at 800-222-1222 or use its online tool. But if your symptoms are severe, call 911 or your local emergency number, or go to the nearest emergency room right away.

When you get Canasa from the pharmacy, the pharmacist will add an expiration date to the label on the packaging. This date is typically 1 year from the date they dispensed the medication.

The expiration date helps guarantee that the medication is effective during this time. The current stance of the Food and Drug Administration (FDA) is to avoid taking expired medications. If you have unused medication that has gone past the expiration date, talk with your pharmacist about whether you might still be able to use it.

Storage

How long a medication remains good to use can depend on many factors, including how and where you store it.

You should store Canasa suppositories at or below room temperature (around 77°F or 25°C). You can also store Canasa in the refrigerator. You should keep Canasa suppositories away from light, heat, or humidity.

Disposal

If you no longer need to take Canasa and have leftover medication, it’s important to dispose of it safely. This helps prevent others, including children and pets, from taking the drug by accident. It also helps keep the drug from harming the environment.

This article provides several useful tips on medication disposal. You can also ask your pharmacist for information about how to dispose of your medication.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.