Azulfidine and Azulfidine EN-tabs (sulfasalazine) are brand-name prescription medications. They’re approved by the Food and Drug Administration (FDA) to treat ulcerative colitis in adults and children ages 6 years and older. Both drugs are approved to:

  • treat mild to moderate ulcerative colitis
  • treat severe ulcerative colitis, in combination with other medications
  • increase the time between flare-ups of ulcerative colitis (this is also called maintaining remission)

Azulfidine EN-Tabs are also FDA-approved to treat:

Azulfidine and Azulfidine EN-Tabs are typically prescribed as long-term treatments.

Here are some fast facts about Azulfidine and Azulfidine EN-tabs:

  • Active ingredient: sulfasalazine
  • Drug class: aminosalicylates (also known as disease-modifying antirheumatic drugs) when prescribed for arthritis
  • Drug forms: oraltablets that you swallow (Azulfidine EN-tabs are a delayed-release form of oral tablet)

As with other drugs, Azulfidine and Azulfidine EN-tabs can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Azulfidine and Azulfidine EN-tabs, including details about their uses, see this article.

Azulfidine and Azulfidine EN-tabs can cause certain side effects (also called adverse effects), some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Azulfidine or Azulfidine EN-tabs in clinical trials:

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

Mild side effects can occur with Azulfidine and Azulfidine EN-tabs. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to the Azulfidine and Azulfidine EN-tabs prescribing information.

Mild side effects that have been reported with Azulfidine and Azulfidine EN-tabs include:

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Azulfidine or Azulfidine EN-tabs and want to tell the FDA about it, visit MedWatch.

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

Azulfidine and Azulfidine EN-tabs may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to the Azulfidine and Azulfidine EN-tabs prescribing information.

If you develop serious side effects while taking Azulfidine or Azulfidine EN-tabs, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

* Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex assigned at birth.
† For more information about this side effect, see “Side effect specifics” below.

Azulfidine and Azulfidine EN-tabs may cause several side effects. Here are some frequently asked questions about the drugs’ side effects and their answers.

I’m taking an Azulfidine or Azulfidine EN-tabs dose of 500 mg. What side effects can I expect?

The side effects that are possible with Azulfidine and Azulfidine EN-tabs are the same regardless of the dose you take. These side effects are described throughout this article.

As with many medications, you may be more likely to get side effects if you take a high dose of Azulfidine or Azulfidine EN-tabs. Your doctor will always prescribe the lowest possible dose to manage your symptoms.

If you’re concerned about side effects with the dosage of Azulfidine or Azulfidine EN-tabs you’ve been prescribed, talk with your doctor.

Will I need blood tests while taking Azulfidine or Azulfidine EN-Tabs?

Yes, your doctor will order various blood tests from time to time while you’re taking Azulfidine or Azulfidine EN-tabs. These blood tests are to check for possible side effects of these medications.

Tests your doctor may order include:

Be sure to keep your appointments for blood tests while taking Azulfidine or Azulfidine EN-tabs. If you have questions about these blood tests, talk with your doctor.

Learn more about some of the side effects that Azulfidine and Azulfidine EN-tabs may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Azulfidine and Azulfidine EN-tabs.

Blood disorders

Azulfidine and Azulfidine EN-tabs can cause blood disorders, although these are rare. In clinical trials, blood disorders that were reported with these medications included:

  • anemia (low level of red blood cells, which carry oxygen around your body)
  • neutropenia (low level of white blood cells, which help your body fight infection)
  • thrombocytopenia (low level of blood cells called platelets, which help blood to clot)
  • agranulocytosis (low levels of all blood cells)

Symptoms of blood disorders may include:

Your doctor will order frequent blood tests to check your blood cell levels while you take Azulfidine or Azulfidine EN-tabs.

What you can do

If you have symptoms of a blood disorder while taking Azulfidine or Azulfidine EN-tabs, contact your doctor right away. They’ll likely order blood tests to check your blood cell levels.

During treatment, be sure to keep your appointments for blood tests. This will allow your doctor to identify any problems with your blood cell levels early. If a problem develops with your blood cell levels, your doctor will likely recommend stopping Azulfidine or Azulfidine EN-tabs. They may also recommend switching to a different medication for your condition.

Serious infection

Azulfidine and Azulfidine EN-tabs can weaken your immune system and increase your risk of getting serious infections, such as pneumonia. Serious infections can sometimes lead to sepsis (an extreme immune response to an infection). In clinical trials, these side effects were rare with Azulfidine and Azulfidine EN-tabs.

Symptoms of a serious infection and sepsis may include:

  • fever
  • cough
  • trouble breathing
  • fast heart rate
  • fatigue

What you can do

Talk with your doctor about your risk of infections before taking Azulfidine or Azulfidine EN-tabs. Be sure to tell them if you have any current infections or infections that keep coming back. Also, tell them about any serious infections you’ve had in the past.

While taking Azulfidine or Azulfidine EN-tabs, be sure to keep your appointments for blood tests. This will allow your doctor to identify any potential problems with your blood cell levels and immune system.

If you have any signs of an infection while taking Azulfidine or Azulfidine EN-tabs, contact your doctor right away. However, if your symptoms feel life threatening, immediately call 911 or your local emergency number.

If you have an infection, your doctor may prescribe medication to treat it. They’ll also likely order blood tests to check your blood cell levels. Your doctor may have you stop taking Azulfidine or Azulfidine EN-tabs until the infection is managed.

Nausea and vomiting

You may have nausea and vomiting while taking Azulfidine or Azulfidine EN-tabs. In clinical trials, these side effects were common in people taking these medications.

Nausea and vomiting typically ease after the first few doses of Azulfidine or Azulfidine EN-tabs.

You may be more likely to have nausea and vomiting with Azulfidine than with Azulfidine EN-tabs. Azulfidine tablets dissolve in your stomach, so the medication may irritate your stomach lining and cause nausea and vomiting. However, Azulfidine EN-tabs have a special coating that allows them to pass through your stomach and into your intestine without irritating your stomach.

What you can do

If you have nausea and vomiting with Azulfidine or Azulfidine EN-tabs, talk with your doctor. They can recommend ways to manage these side effects, such as having you take the medication with or after food.

If you have nausea and vomiting that doesn’t ease after your first few doses, talk with your doctor. Your doctor may lower your dosage of Azulfidine or Azulfidine EN-tabs for a few days. Then they may increase your dosage slowly again.

If you take Azulfidine and you still have bothersome nausea and vomiting, ask your doctor if switching to Azulfidine EN-tabs could be a good option for you.

Allergic reaction

As with most drugs, Azulfidine and Azulfidine EN-tabs can cause an allergic reaction in some people.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Azulfidine or Azulfidine EN-tabs. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Be sure to talk with your doctor about your health history before you take Azulfidine or Azulfidine EN-tabs. They may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:

Porphyria. If you have an inherited blood disorder called porphyria, Azulfidine and Azulfidine EN-tabs could cause an acute attack of porphyria. Due to this risk, your doctor typically will not prescribe Azulfidine or Azulfidine EN-tabs. Ask your doctor what other medications may be better options for you.

Blockage in your intestine or urinary tract. If you have a blockage in your intestinal tract or urinary tract, Azulfidine and Azulfidine EN-tabs could make it worse. Due to this risk, your doctor typically will not prescribe Azulfidine or Azulfidine EN-tabs. Ask your doctor what other medications may be better options for you.

Liver or kidney problems. Azulfidine and Azulfidine EN-tabs can cause liver and kidney problems. If you already have a liver or kidney problem, these medications could make your condition worse. Talk with your doctor about whether Azulfidine or Azulfidine EN-tabs are right for you. If you do take one of these medications, your doctor will order frequent blood tests and urine tests to check your liver and kidney function.

Blood disorders. Azulfidine and Azulfidine EN-tabs can cause blood disorders such as low levels of red blood cells or white blood cells. If you already have a blood disorder, these medications could make your condition worse. Talk with your doctor about whether Azulfidine or Azulfidine EN-tabs are right for you. If you do take one of these medications, your doctor will order frequent blood tests to check your blood cell levels.

G6PD deficiency. Glucose-6 phosphate dehydrogenase (G6PD) is a protein that helps keep your red blood cells healthy. If you have G6PD deficiency, you may have a raised risk of hemolytic anemia (red blood cell breakdown) with Azulfidine and Azulfidine EN-tabs. Talk with your doctor about whether Azulfidine or Azulfidine EN-tabs are right for you. If you do take these medications, your doctor will order frequent blood tests to check your red blood cell level.

Asthma. If you have asthma, taking Azulfidine or Azulfidine EN-tabs could worsen your symptoms. Your doctor may monitor your asthma more often after you start taking one of these medications. Be sure to tell your doctor if you have asthma before starting treatment with Azulfidine or Azulfidine EN-tabs.

Allergic reaction. Be sure to tell your doctor if you have a history of allergic reactions. If you’ve had an allergic reaction to Azulfidine, Azulfidine EN-tabs, or any of their ingredients, your doctor will likely not prescribe Azulfidine or Azulfidine EN-tabs.

In addition, your doctor will likely not prescribe Azulfidine or Azulfidine EN-tabs if you’ve had an allergic reaction to sulfonamide or salicylate medications. An example of a sulfonamide is Bactrim (sulfamethoxazole). An example of a salicylate is Lialda (mesalamine). Ask your doctor what other medications may be better options for you.

Alcohol with Azulfidine or Azulfidine EN-tabs

Azulfidine and Azulfidine EN-tabs don’t interact with alcohol. However, drinking alcohol with these medications could increase your risk of side effects such as headache and nausea. It could also increase your risk of liver problems with these medications.

If you drink alcohol, talk with your doctor about how much (if any) is safe to consume while taking Azulfidine or Azulfidine EN-tabs.

Pregnancy and breastfeeding while taking Azulfidine or Azulfidine EN-tabs

Below are details about taking Azulfidine or Azulfidine EN-tabs during pregnancy or while breastfeeding.

Pregnancy while taking Azulfidine or Azulfidine EN-tabs

It’s not known if Azulfidine or Azulfidine EN-tabs are safe to take during pregnancy. In animal trials, sulfasalazine (the active drug in Azulfidine and Azulfidine EN-tabs) didn’t cause fetal harm when given to pregnant females. However, animal trials don’t always predict what will happen in humans.

There have been reports of certain congenital anomalies (commonly known as birth defects), such as spina bifida, in children born to females* who took sulfasalazine during pregnancy. However, rather than being caused by the drug, these congenital anomalies may have occurred because sulfasalazine reduces the absorption of folic acid supplements. Folic acid supplements are recommended during pregnancy to help reduce the risk of certain congenital anomalies.

If you’re pregnant or planning to become pregnant, talk with your doctor about the risks and benefits of taking Azulfidine or Azulfidine EN-tabs. If you do decide to take one of these medications, your doctor may recommend taking folic acid at a dosage that’s higher than typically prescribed.

* Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.

Breastfeeding while taking Azulfidine or Azulfidine EN-tabs

Sulfasalazine (the active drug in Azulfidine and Azulfidine EN-tabs) can pass into breast milk. It’s not known what effect this may have on a child who’s breastfed. However, some females* taking these medications have reported diarrhea or bloody stools in their children who were breastfed.

If you’re breastfeeding or plan to breastfeed, talk with your doctor about the risks and benefits of taking Azulfidine or Azulfidine EN-tabs. They can advise you on the best way to feed your child.

* Sex and gender exist on spectrums. Use of the term “female” in this article refers to sex assigned at birth.

Side effects of Azulfidine and Azulfidine EN-tabs are typically mild and get better with continued use of the drug. However, some rare and serious side effects are also possible with these medications.

If you’d like to learn more about Azulfidine and Azulfidine EN-tabs, talk with your doctor or pharmacist. They can help answer any questions you have about side effects of taking the drugs.

Besides talking with your doctor, you can do some research on your own. These articles might help:

  • More information about Azulfidine and Azulfidine EN-tabs. For details about other aspects of Azulfidine and Azulfidine EN-tabs, refer to this article.
  • A look at your condition. For details about ulcerative colitis, this list of related articles might be helpful. For details about arthritis, see our arthritis hub as well as this list of rheumatology articles.

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.