If you have ulcerative colitis (UC) or a certain type of arthritis, your doctor might suggest Azulfidine or Azulfidine EN-tabs (sulfasalazine) as a treatment option for you.

Azulfidine and Azulfidine EN-tabs are prescription medications used to treat UC in adults. Azulfidine and Azulfidine EN-tabs may be used alone for treating mild or moderate UC. For treating severe UC, they may be used with other drugs.

Azulfidine EN-tabs also treat rheumatoid arthritis in adults and polyarticular juvenile idiopathic arthritis in some children.

Azulfidine and Azulfidine EN-tabs come as tablets that you swallow. For more information about these drugs, including details about their uses, see this in-depth article.

Like other drugs, Azulfidine and Azulfidine EN-tabs can cause mild or serious side effects (also called adverse effects). Keep reading to learn more.

Some people may experience mild or serious side effects during their treatment with Azulfidine or Azulfidine EN-tabs. Examples of commonly reported side effects for these drugs may include:

These are just a few of the more common side effects reported by people who took Azulfidine or Azulfidine EN-tabs in studies. To learn about more side effects these drugs may cause, see the sections below. You can also view the drugs’ full prescribing information.

Like most medications, Azulfidine and Azulfidine EN-tabs may cause mild side effects. Examples of mild side effects reported with these drugs include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And do not stop using Azulfidine or Azulfidine EN-tabs unless your doctor recommends it.

Azulfidine and Azulfidine EN-tabs may cause mild side effects other than the ones listed above. See the drugs’ prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Azulfidine or Azulfidine EN-tabs, visit MedWatch.

Serious side effects have occurred with Azulfidine and Azulfidine EN-tabs. It’s not known how often serious side effects happened in the drugs’ studies. But most people who take Azulfidine or Azulfidine EN-tabs don’t have serious side effects.

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

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 if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section below.

Get answers to some frequently asked questions about the side effects of Azulfidine and Azulfidine EN-tabs.

Can Azulfidine and Azulfidine EN-tabs cause long-term side effects?

It’s possible. Long-term side effects were reported in studies of Azulfidine and Azulfidine EN-tabs. These included:

Kidney or liver problems could occur at any time during your treatment with Azulfidine or Azulfidine EN-tabs. And in rare cases, these side effects may not be reversible, even if you stop your treatment.

To learn more about long-term side effects of Azulfidine or Azulfidine EN-tabs, talk with your doctor or pharmacist.

Can Azulfidine or Azulfidine EN-tabs cause sexual side effects?

Yes, sexual side effects in males* have been reported with Azulfidine and Azulfidine EN-tabs.

Specifically, these drugs can cause low sperm count. To learn more, see the “Side effects explained” section below.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Will stopping my Azulfidine or Azulfidine EN-tabs treatment cause withdrawal symptoms?

It’s not likely. Withdrawal symptoms weren’t reported in studies of Azulfidine and Azulfidine EN-tabs. (Withdrawal symptoms are side effects that can happen when you stop taking a drug that your body has become dependent on.)

Keep in mind that if you stop taking Azulfidine or Azulfidine EN-tabs, symptoms of your condition may come back or get worse. But this is different than having withdrawal symptoms.

If you have questions about stopping your treatment with Azulfidine or Azulfidine EN-tabs, talk with your doctor or pharmacist.

Learn more about some of the side effects Azulfidine and Azulfidine EN-tabs may cause.

Blood disorders

Taking Azulfidine or Azulfidine EN-tabs may cause blood disorders in some people. It’s not known exactly how often these side effects occurred in studies, but they’re thought to be rare.

Blood disorders reported in people taking Azulfidine and Azulfidine EN-tabs include:

  • leukopenia (low levels of leukocytes, a type of white blood cell)
  • thrombocytopenia (low levels of platelets, a type of cell that helps with blood clotting)
  • anemia (low levels of red blood cells)
  • agranulocytosis (dangerously low levels of white blood cells)

Depending on the type of disorder and how severe it is, you may not have any noticeable symptoms. Often, changes in blood cell levels are first noticed with a blood test. But in some cases, it’s possible to have symptoms. These may include:

  • feeling lightheaded or dizzy
  • frequent infections or an infection that won’t go away
  • fatigue (low energy)
  • unusual bruising or bleeding
  • weakness

What might help

Your doctor will likely monitor you for blood disorders while you’re taking Azulfidine or Azulfidine EN-tabs. They can tell you more about how often they’ll order lab tests to check for any problems.

If you notice any of the symptoms listed above, call your doctor right away. If you do have a blood disorder, your doctor may prescribe treatment for it. They may also have you temporarily or permanently stop taking Azulfidine or Azulfidine EN-tabs.

Serious infection

Serious infections, such as pneumonia or sepsis, can occur with Azulfidine or Azulfidine EN-tabs. It’s not known how often these infections occurred in studies of the drugs, but they’re thought to be rare. In extremely rare cases, these infections have been fatal.

Symptoms of pneumonia can include:

Symptoms of sepsis may include:

What might help

Call your doctor right away if you notice symptoms of an infection while taking Azulfidine or Azulfidine EN-tabs. If they confirm you have a serious infection, they’ll likely have you stop taking Azulfidine or Azulfidine EN-tabs. They can also prescribe treatment for your infection. In some cases, an infection may require treatment in a hospital.

Low sperm count

Males* taking Azulfidine or Azulfidine EN-tabs may experience low sperm count and infertility (not being able to conceive). It’s not known how often this side effect occurred in studies, but it may be common.

Low sperm count and infertility from these drugs may be reversible, meaning it goes away once you stop your treatment.

What might help

If you’re concerned about low sperm count and infertility caused by Azulfidine or Azulfidine EN-tabs, talk with your doctor. Stopping treatment with the drug appears to reverse this side effect. Your doctor can tell you about other treatment options for your condition, including drugs that may not cause sexual side effects.

Severe skin reactions

Severe skin reactions are possible side effects of Azulfidine and Azulfidine EN-tabs. It’s not known exactly how often these side effects occurred in studies, but they’re thought to be rare. In very rare cases, these reactions can be life threatening.

These reactions are most common during your first month of treatment.

Severe skin reactions reported with Azulfidine and Azulfidine EN-tabs include:

Symptoms of a severe skin reaction can vary but may include:

  • blisters on your eyes, lips, mouth, or skin
  • fever
  • flu-like symptoms
  • rash that continues to get worse
  • red or discolored skin
  • severe rash
  • skin that burns or is painful
  • skin peeling

What might help

If you think you’re having a severe skin reaction, stop taking Azulfidine or Azulfidine EN-tabs and call your doctor right away. In rare cases, these reactions can be life threatening and may require treatment in a hospital. If your symptoms feel life threatening, seek emergency medical care right away.

If you have a severe skin reaction to Azulfidine or Azulfidine EN-tabs, your doctor will likely have you stop taking it. They can discuss other treatment options with you.

Allergic reaction

Like most drugs, Azulfidine and Azulfidine EN-tabs can cause an allergic reaction in some people. It’s not known exactly how often these reactions occurred in clinical trials, though.

Symptoms can be mild or serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • 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 might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest an over-the-counter oral antihistamine, such as Benadryl (diphenhydramine), or a topical product, such as hydrocortisone cream, to manage your symptoms.

If your doctor confirms you had a mild allergic reaction to Azulfidine or Azulfidine EN-tabs, they’ll decide if you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you had a serious allergic reaction to Azulfidine or Azulfidine EN-tabs, they may have you switch to a different treatment.

Keeping track of side effects

During your Azulfidine or Azulfidine EN-tabs treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon after starting that dose you had the side effect
  • what your symptoms were from the side effect
  • how it affected your daily activities
  • what other medications you were also taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help your doctor learn more about how Azulfidine or Azulfidine EN-tabs affect you. And your doctor can use this information to adjust your treatment plan if needed.

Azulfidine or Azulfidine EN-tabs may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before taking Azulfidine or Azulfidine EN-tabs. The list below includes factors to consider.

Blockage in your intestinal tract or urinary tract. Doctors likely will not prescribe Azulfidine or Azulfidine EN-tabs if you have a blockage in your intestinal tract or urinary tract. This is because the drug may cause side effects that can affect digestion and urination. Examples of these side effects include belly pain, nausea and vomiting, or kidney problems.

Porphyria. If you have a condition called porphyria, your doctor will likely not prescribe Azulfidine or Azulfidine EN-tabs for you. Taking either of these drugs could cause an acute porphyria attack. You can talk with your doctor about other treatments that may be safer for you.

Sulfonamide or salicylate allergy. Doctors likely will not prescribe Azulfidine or Azulfidine EN-tabs if you have an allergy to sulfonamide or salicylate medications. Examples of sulfonamides include sulfamethoxazole/trimethoprim (Bactrim, Septra). An example of a salicylate is bismuth subsalicylate (Pepto-Bismol). If you have an allergy to either of these types of medications, ask your doctor about other possible treatment options.

Blood disorder. Azulfidine and Azulfidine EN-tabs can cause certain blood disorders. If you already have a blood disorder such as anemia (low levels of red blood cells), taking either of these drugs could make your condition worse. Your doctor can help determine whether Azulfidine or Azulfidine EN-tabs are safe for you.

Kidney problems. Azulfidine and Azulfidine EN-tabs can cause kidney problems. If you already have kidney problems, such as chronic kidney disease, taking either of these drugs could make your condition worse. Talk with your doctor about whether Azulfidine or Azulfidine EN-tabs may be safe for you.

Liver problems. Azulfidine and Azulfidine EN-tabs can cause liver problems. If you already have liver problems, such as hepatitis, taking one of these drugs could worsen your condition. Your doctor can help determine whether Azulfidine or Azulfidine EN-tabs are safe for you.

Allergic reaction. If you’ve had an allergic reaction to Azulfidine or Azulfidine EN-tabs or any of their ingredients, your doctor will likely not prescribe Azulfidine or Azulfidine EN-tabs. Ask your doctor what other medications are better options for you.

Alcohol use and Azulfidine or Azulfidine EN-tabs

There are no known interactions between Azulfidine or Azulfidine EN-tabs and alcohol.

However, alcohol may raise your risk of certain side effects from these drugs or make the side effects worse. Examples of these side effects include:

  • nausea
  • headache
  • worsening kidney problems
  • worsening liver problems

If you drink alcohol, talk with your doctor about how much is safe for you to drink during your treatment with Azulfidine or Azulfidine EN-tabs.

Pregnancy and breastfeeding while taking Azulfidine or Azulfidine EN-tabs

It’s not known whether it’s safe to take Azulfidine or Azulfidine EN-tabs while pregnant or breastfeeding. See below for details.

Pregnancy. There are conflicting reports about whether sulfasalazine, the active drug in Azulfidine and Azulfidine EN-tabs, may cause problems with fetal development (commonly known as birth defects). But these fetal development problems may not be a direct side effect of the drug. Instead, they may have occurred because sulfasalazine reduces your body’s ability to absorb folic acid supplements. (Folic acid is recommended during pregnancy to help reduce the risk of certain fetal development problems.)

Breastfeeding. Sulfasalazine (the active drug in Azulfidine and Azulfidine EN-tabs) can pass into breast milk. It’s unknown what effects this could have, but side effects (including diarrhea and bloody stools) have been reported in children exposed to sulfasalazine through breast milk. It’s not known if sulfasalazine was the cause of these side effects.

If you’re pregnant or breastfeeding, or planning to become pregnant or breastfeed, talk with your doctor before using Azulfidine or Azulfidine EN-tabs.

Like most drugs, taking Azulfidine or Azulfidine EN-tabs can cause side effects. This may include serious side effects in rare cases.

If you’re interested in learning more about taking Azulfidine or Azulfidine EN-tabs, talk with your doctor or pharmacist. Asking questions can help you feel confident about your treatment. Some questions you may want to ask include:

  • Are there ways I can lower my risk for side effects from Azulfidine or Azulfidine EN-tabs?
  • If I develop side effects during my treatment, can I take a lower dose?
  • Do other medications I take raise my risk of side effects with Azulfidine or Azulfidine EN-tabs?

If you have ulcerative colitis or rheumatoid arthritis (RA), consider signing up for Healthline’s IBD newsletter or RA newsletter for advice about managing these conditions.

Q:

Do side effects caused by Azulfidine and Azulfidine EN-tabs vary depending on the dose?

Anonymous

A:

It’s possible. Reports have shown that larger doses of Azulfidine and Azulfidine EN-tabs may increase the risk of side effects. This is especially true with a dosage of more than 4,000 milligrams per day.

If you’re concerned about your risk of side effects with your prescribed dose of Azulfidine or Azulfidine EN-tabs, talk with your doctor or pharmacist.

Elizabeth Scheffel, PharmDAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Disclaimer: Healthline 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.