Nucala (mepolizumab) is a prescription biologic used to treat a certain type of asthma and other immune-related conditions. Nucala can cause side effects that range from mild to serious, including headache and back pain.

Specifically, Nucala is a biologic drug prescribed to treat:

Nucala cannot stop an asthma attack. It’s important to contact a doctor right away if you do not see a reduction in asthma symptoms or your symptoms get worse after you start Nucala treatment.

The active ingredient in Nucala is mepolizumab. (An active ingredient is what makes a drug work.) The drug comes as a liquid solution that you inject under the skin using a prefilled, disposable syringe or autoinjector.

Keep reading to learn about the common, mild, and serious side effects Nucala can cause. For a general overview of the drug, including details about its uses, see this article.

Below are a few of the more common side effects reported by people who took Nucala in studies. These side effects can vary depending on what condition the drug is being used to treat and may not happen to everyone.

More common side effects in people taking Nucala for eosinophilic asthma, hypereosinophilic syndrome, and eosinophilic granulomatosis with polyangiitis include:

More common side effects in people taking Nucala for chronic rhinosinusitis with nasal polyps include:

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

Using Nucala to treat eosinophilic asthma, hypereosinophilic syndrome, and eosinophilic granulomatosis with polyangiitis can cause mild side effects. These include:

Mild side effects have been reported while using Nucala to treat chronic rhinosinusitis with nasal polyps. These include:

In most cases, these side effects should be temporary. And some may be easily managed. But if you have ongoing, bothersome, or severe symptoms, talk with your doctor or pharmacist. And do not stop using Nucala unless your doctor recommends it.

Nucala may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

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

Serious side effects have been reported with Nucala. These include:

If you develop serious side effects with Nucala, 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.

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

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 Nucala, visit MedWatch.

Get answers to some frequently asked questions about Nucala’s side effects.

Does Nucala cause long-term side effects?

It’s possible. Long-term side effects include those that may start at any time you’re taking a drug, even if you’ve taken it for a long time. It also includes side effects that may not go away, even after you stop taking the drug.

Shingles was reported in all Nucala studies. And shingles may cause long-term effects, such as nerve damage. Because the drug can lower your immune system‘s ability to fight off infections, such as shingles, your doctor may recommend you get a shingles vaccine before starting Nucala. This may decrease your risk of getting shingles, but it won’t eliminate it.

A 2019 study on the long-term effects of Nucala for treating asthma showed no additional safety concerns during an average of 3.5 years of treatment.

Talk with your doctor to learn more about possible long-term side effects of Nucala and how to reduce your risk.

How long do side effects of Nucala usually last?

Some side effects of Nucala, such as headache, diarrhea, or fever, may go away after a few days to a few weeks. Other side effects may last throughout your Nucala treatment, such as eczema and joint and muscle pain.

If your side effects are bothersome or ongoing, talk with your doctor about next steps. Suddenly stopping Nucala may cause an asthma attack. So do not stop taking the drug without talking with your doctor first.

Can Nucala make me tired?

Yes, Nucala may cause you to feel tired. Studies showed that fatigue (low energy) was a common side effect of Nucala. Following a regular sleep routine, eating nutritiously, and exercising, as advised by your doctor, may help reduce this symptom.

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

Back pain

Back pain was a common side effect reported in studies of Nucala when used to treat eosinophilic asthma, hypereosinophilic syndrome, and eosinophilic granulomatosis with polyangiitis. Back pain may include soreness, stiffness, and stabbing or pinching sensations.

Factors that can increase the risk of back pain with Nucala are unknown since studies didn’t look at what was causing it.

What might help

If you have muscle pain during Nucala treatment, consider over-the-counter muscle rubs or patches to help relieve your symptoms. Choose ones with menthol or lidocaine but not aspirin or salicylate, as these can cause asthma to flare up. It’s also best to talk with your doctor. They’ll likely recommend an office visit to discuss treatment options.

Joint pain

Joint pain was a common side effect reported in studies of Nucala when used to treat chronic rhinosinusitis with nasal polyps. Joint pain may cause symptoms such as stiffness, tenderness, swelling, and warmth to the touch.

Factors that can increase the risk of joint pain with Nucala are unknown because studies did not look at what was causing joint pain.

What might help

Elevating a swollen joint or applying a cold pack to the area may help relieve joint pain. But it’s important to talk with your doctor about joint pain from Nucala, especially if your joint is warm to the touch. A warm joint may be caused by an infection. Your doctor will likely recommend an office visit to discuss your symptoms and treatments options.

Allergic reaction

As with most drugs, Nucala can cause an allergic reaction in some people. Most of the time, these reactions happen a few hours after injecting a dose. But they can sometimes take a few days to appear.

Symptoms can be mild to serious and may include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin (usually 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 a treatment to manage your symptoms. Examples include:

  • an oral antihistamine, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Nucala, they’ll decide whether 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’ve had a serious allergic reaction to Nucala, they may have you switch to a different treatment.

Keeping track of side effects

During your Nucala treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug 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 you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Nucala affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before starting Nucala.

Warnings

Nucala can sometimes cause harmful effects in people with certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Nucala is a good treatment option for you.

Talk with your doctor about your health history before starting Nucala. Be sure to tell them if any of the following factors apply to you:

Nucala cannot stop an asthma attack. It’s a good idea to keep your rescue inhaler with you until you see how Nucala affects your asthma. See a doctor right away if your asthma gets worse or doesn’t improve after you start Nucala.

Alcohol and Nucala

There are no known interactions between alcohol and Nucala. But if you have headaches or fatigue (low energy) during Nucala treatment, alcohol may make those side effects worse.

If you drink alcohol and have questions about consuming it during Nucala treatment, talk with your doctor or pharmacist.

Pregnancy and breastfeeding with Nucala

Before starting Nucala treatment, it’s important to talk with your doctor if you’re pregnant, breastfeeding, or planning to be either.

Pregnancy

It’s not known whether it’s safe to use Nucala during pregnancy. Biologic drugs, such as Nucala, may affect the fetus as pregnancy progresses into the second or third trimester. So there might be more risk of harm to the fetus in the later months of pregnancy.

If you’re pregnant or planning to become pregnant, talk with your doctor before starting treatment with Nucala.

If you use Nucala while pregnant, consider signing up for the manufacturer’s pregnancy registry by visiting the website or calling 877-311-8972. A pregnancy registry collects information about the safety of certain drugs when used during pregnancy.

Breastfeeding

It isn’t known whether Nucala is safe to use while breastfeeding. It’s unknown whether the drug passes into breast milk, how it might affect a child who’s breastfed, or how it affects milk production.

If you’re breastfeeding or planning to, talk with your doctor before starting this medication.

As with most drugs, Nucala can cause several side effects that range from mild to serious. However, some are temporary and go away after a few days to weeks. If you have questions about side effects that Nucala can cause, talk with your doctor.

Examples of questions to help get you started include:

  • Is my risk of allergic reaction higher when I first begin treatment?
  • Do I have a higher risk of side effects than others?
  • What side effects am I most likely to experience?
  • When should I call about the side effects I’m having?
  • Will side effects go away on their own?

To learn more about Nucala, see these articles:

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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.