Onureg (azacitidine) can cause side effects that range from mild to serious. More common side effects include weakness, joint pain, and nausea. If side effects from Onureg become difficult to tolerate, talk with your doctor about coping tips or other treatment options.

If you have acute myeloid leukemia (AML), your doctor might suggest Onureg as a treatment option for you. Onureg is a prescription drug that’s used to treat AML in adults in certain situations. It’s typically taken long term.

Onureg comes as a tablet that you swallow. Its active ingredient is azacitidine. An active ingredient is what makes a drug work.

Keep reading to learn about the common, mild, and serious side effects Onureg can cause. For more information about Onureg, including details about its use, see this in-depth Onureg article.

Onureg can cause certain side effects, some more common than others. These side effects may be temporary, lasting a few days to weeks. Talk with your doctor if side effects do not go away, get worse, or become too difficult for you to tolerate.

Onureg’s commonly reported side effects include:

To learn more about some of these side effects, see the “Side effect specifics” section.

This section lists the mild side effects of Onureg, which can occur in some people who take this drug. A side effect that starts out mild may get worse, so talk with your doctor about any side effects you have.

Examples of mild side effects that have been reported with Onureg include:

  • abdominal pain
  • constipation or diarrhea
  • pain in the arms or legs
  • dizziness
  • low appetite
  • weakness or fatigue (low energy)
  • joint pain
  • nausea and vomiting

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 taking Onureg unless your doctor recommends it.

Onureg may cause mild side effects other than the ones listed above. See the Onureg prescribing information for details.

For details about some of these side effects, see the “Side effect specifics” section.

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 Onureg, visit MedWatch.

Onureg may cause serious side effects. Some of these are also common, such as low levels of neutrophils. The following list may not include all possible serious side effects of the drug. For more information, you can refer to the drug’s prescribing information.

If you develop serious side effects while taking Onureg, 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.

Serious side effects that have been reported with Onureg include:

For more information about some of these side effects, see the “Side effect specifics” section.

* This side effect was reported after Onureg became available on the market.

Below are answers to some frequently asked questions about Onureg’s side effects.

Is Onureg safe for older adults?

Overall, yes. In studies, Onureg side effects in older adults (ages 65 years and older) were similar to those reported in other adults. But Onureg should be used with caution in people with certain health issues, including liver and kidney problems. For more information about these and other possible concerns, see the “Precautions for Onureg” section.

If you have questions about the safety of Onureg given your age, talk with your doctor.

How long do the side effects of Onureg last? Are there any long-term side effects?

Some Onureg side effects, such as nausea, vomiting, and fatigue, may be temporary. These side effects often occur early in treatment and may ease as your body adjusts to the medication.

Long-term side effects of Onureg are possible. These are side effects that either continue throughout treatment and beyond or start after extended use of the drug. A key example is myelosuppression, which includes low levels of neutrophils (white blood cells) and platelets. Myelosuppression can increase the risk of infection or bleeding. While these effects are often reversible after treatment ends, recovery may take time. In some cases, the risk of infection continues​.

You can learn more about these Onureg side effects in the “Side effect specifics” section. If you have questions about your risk of long-term side effects, talk with your doctor for more information.

Does Onureg cause hair loss?

Hair loss was not reported as a side effect in Onureg clinical trials. However, many people taking Onureg have previously undergone chemotherapy, which is a common cause of hair loss.

Chemotherapy-induced hair loss can sometimes last for months or even years after treatment ends, depending on the specific chemotherapy drug.

If you experience hair loss or thinning while taking Onureg, talk with your doctor. They can help determine whether your hair loss is related to Onureg, previous treatments, or another health condition. They can also suggest strategies or treatments to help manage hair loss.

Are the side effects of intravenous (IV) azacitidine the same as those of the Onureg tablet?

The active ingredient in Onureg is azacitidine. Onureg comes only as a tablet you swallow, but other forms of azacitidine are available with different brand names. Some of the side effects between forms are the same. But other azacitidine forms may have additional side effects.

For example, a serious side effect of an azacitidine injection given intravenously (into a vein) or subcutaneously (just under the skin) is tumor lysis syndrome. This condition can occur when tumors break down very fast and release substances such as phosphate and uric acid into the bloodstream. Potential complications include kidney damage or heart problems.

Tumor lysis syndrome was reported after injectable azacitidine became available on the market. This side effect did not occur in studies of Onureg. For more information, see Onureg’s prescribing information.

The manufacturer does not recommend substituting one form of azacitidine for another. If you have questions about other forms of azacitidine and their side effects, talk with your doctor.

Learn more about some of the side effects Onureg may cause.

Weakness or fatigue

In studies of Onureg, weakness and fatigue were common side effects. Weakness means you feel less strength in your muscles. Fatigue means you have less energy and feel more sleepy than usual. With these side effects, you may feel tired or that your strength has decreased.

What you can do

Here are a few things to try that may help decrease weakness or fatigue:

Talk with your doctor about other ways to manage your strength and energy levels while taking Onureg.

Low levels of neutrophils and platelets

Low levels of certain blood cells were a common side effect in studies of Onureg.

Onureg can reduce the level of neutrophils, a type of white blood cell needed to fight infection. A symptom of low neutrophil levels is frequent or severe infections.

Onureg can also reduce the level of platelets needed for blood clotting. A symptom of problems with blood clotting is frequent bruising.

What you can do

Before you start taking Onureg, your doctor will check your blood cell levels. And you’ll continue to have blood tests during your treatment to monitor these levels.

If your levels of neutrophils or platelets become low, your doctor may temporarily pause or decrease your dose of Onureg until your levels return to a more usual level. Or they may recommend you take a different medication.

Talk with your doctor right away if you notice the following symptoms of infection due to low neutrophil levels:

Nausea and vomiting

In studies of Onureg, two common side effects were nausea and vomiting. These side effects ranged from mild to severe.

What you can do

During your first two treatment cycles* of Onureg, your doctor will likely give you medication to help prevent nausea and vomiting. Your doctor will also help you manage these side effects while you’re taking Onureg. Two medications your doctor may prescribe are metoclopramide (Reglan) and ondansetron (Zofran).

If you have severe nausea and vomiting, your doctor may pause your Onureg treatment temporarily. They may also decide to decrease the number of days that you take Onureg each month. If your nausea and vomiting don’t go away, they may recommend a treatment other than Onureg for your condition.

Note: If you vomit right after taking an Onureg tablet, do not take another one. Take your next dose at the regularly scheduled time. If you have questions about this, talk with your doctor for more information.

* You’ll take Onureg for 14 days and then stop taking it for 14 days. This 28-day period is called a cycle. For more information, see this Onureg and dosage overview.

Joint pain

Joint pain was a common side effect in studies of Onureg. It can range from mild to severe. This pain may occur in smaller joints, such as those in your fingers. It can also occur in larger joints, such as your knees or the joints of your hips.

What you can do

Here are a few things to try that may help reduce any joint pain that you’re having:

Note: Before you take any pain reliever or anti-inflammatory, talk with your doctor. They can recommend products that do not interact with Onureg.

For more ways to reduce joint pain during Onureg treatment, talk with your doctor.

Allergic reaction

Like most drugs, Onureg can cause an allergic reaction in some people. This side effect did not occur in Onureg studies, but there have been reports since the drug became available on the market.

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 you can do

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. To manage your symptoms, they may suggest an over-the-counter antihistamine that you take by mouth, such as diphenhydramine (Benadryl). Or they may recommend a product you apply to your skin, such as hydrocortisone cream.

If your doctor confirms you had a mild allergic reaction to Onureg, they’ll decide if you should continue taking 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 Onureg, they may have you switch to a different treatment.

Keeping track of side effects

During your Onureg 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 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 Onureg affects you. And your doctor can use this information to adjust your treatment plan if needed.

Onureg 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 you take Onureg. The list below includes factors to consider.

Liver problems: Onureg hasn’t been studied in people with serious liver problems. If you have liver problems, your doctor may test your liver function to find out if Onureg is safe for you to take. Before taking Onureg, be sure to tell your doctor about any liver problems you have.

Low levels of neutrophils or platelets: Onureg may cause low levels of neutrophils or platelets. This can lead to a serious fever or cause problems with blood clotting. If you already have a low level of neutrophils or platelets, your doctor may wait to start your Onureg treatment.

Myelodysplastic syndromes (MDS): Serious side effects and even death have been reported in studies of Onureg for MDS (a type of bone marrow cancer). Onureg should not be used to treat MDS. If you have MDS, your doctor will recommend other medication options for your condition.

Kidney problems: Onureg hasn’t been studied in people with serious kidney problems. So if you already have kidney damage, talk with your doctor about whether Onureg is a good option for you. Your doctor may test your kidney function before making a recommendation about Onureg.

Allergic reaction: If you’ve had an allergic reaction to Onureg or any of its ingredients, your doctor will likely not prescribe Onureg. Ask your doctor what other medications are better options for you.

Alcohol and Onureg

There is no known interaction between Onureg and alcohol. But both alcohol and Onureg can cause some of the same effects, such as nausea or dizziness.

If you drink alcohol, talk with your doctor to find out how much is safe to consume during treatment with Onureg.

Pregnancy and breastfeeding while taking Onureg

Onureg is not safe to take during pregnancy or while breastfeeding.

Pregnancy

Due to a risk of fetal harm, your doctor will likely not prescribe Onureg if you’re pregnant or planning to become pregnant. If you or your sexual partner can become pregnant, it’s recommended that you use effective birth control while taking Onureg.

For females, the manufacturer recommends using birth control for at least 6 months after their last Onureg dose. And males are advised to use birth control for at least 3 months after their last Onureg dose.

Before you start taking Onureg, be sure to talk with your doctor about effective birth control options.

Note: In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. Learn more about the difference between sex and gender.

Breastfeeding

Onureg hasn’t been studied during breastfeeding. But it’s not recommended that you breastfeed while taking this drug.

If you plan to breastfeed, your doctor may advise you to wait a certain amount of time after you stop taking Onureg. The manufacturer of Onureg recommends waiting 1 week after your final Onureg dose. But be sure to follow your doctor’s recommendations.

Talk with your doctor about safe ways to feed a child who is breastfed while you’re taking Onureg.

Onureg is prescribed to treat certain kinds of AML. But like most drugs, it can cause side effects. Here are a few questions you might want to ask your doctor about Onureg side effects:

  • Will Onureg affect my ability to eat as I usually would?
  • Which blood tests will I need to get while I am taking Onureg?
  • What kinds of birth control do I need to use while I take Onureg?
  • How can I tell if I have a serious infection as a side effect of Onureg?
  • My kidney problems are mild. Can I still take Onureg?

Q:

Can Onureg cause serious pneumonia?

Anonymous

A:

Pneumonia is a serious infection in your lungs. Studies of Onureg found that pneumonia was a common side effect. While pneumonia occurred more often than other side effects, not everyone taking Onureg will develop this infection.

In general, your immune system will not be as strong as usual while you take Onureg. So you’re more likely to get an infection during treatment. If you have symptoms of pneumonia or other infections, contact your doctor right away. They may pause your dose and check your white blood cell level.

Once your doctor has determined the cause of your infection, they’ll recommend the right treatment options to help you get better.

The Healthline Pharmacist TeamAnswers 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.