5 Nucala Side Effects and How to Manage Them

Nucala (mepolizumab) is an injectable medication that lowers the amount of eosinophils in your body. Eosinophils are a type of white blood cell involved in lung inflammation. Because of how Nucala works, it’s used to treat several conditions caused by high eosinophils, such as severe eosinophilic asthma.

Nucala’s asthma benefits outweigh its risks in the large majority of cases. After all, its side effects are generally mild and easy to manage. But it’s still a good idea to be familiar with what to expect before you start the treatment.

Nucala side effects at a glance

A number of Nucala side effects have been reported in clinical trials and real-world studies. Some are common and relatively mild, while others are more substantial.

The most common side effects of Nucala include:

• Headache

• Injection site reactions, including redness, itching, or burning

• Back, throat, and joint pain

• Fatigue, or tiredness

• Muscle spasms

Rare, but potentially serious side effects include:

• Serious infections, including herpes zoster (shingles)

• Allergic reactions

Below, we'll go over the top five Nucala side effects to know about and what you can do to manage them. Keep in mind that you should let your healthcare provider know about any concerning symptoms you develop while receiving Nucala — even if they’re not listed here.

1. Injection site reactions

Like any injectable medication, Nucala may cause reactions in the area where the needle enters the skin. This includes:

• Pain

• Redness

• Swelling

• Itching

• Burning

These side effects usually develop within a few hours of the injection. But they can also happen a few days after getting Nucala. Mild injection site reactions are common and they don’t mean that you’re allergic to Nucala. These reactions usually go away on their own over time. 

There are a few steps you can take to limit symptoms in the meantime. You can apply warm and cold compresses over the injection site area for 10 to 20 minutes at a time. Warm compresses help with muscle irritation, while cold compresses help with symptoms such as skin redness and swelling.

Over-the-counter (OTC) pain medications,such as acetaminophen (Tylenol), can help with pain and antihistamines, such as diphenhydramine (Benadryl), can reduce itching and swelling, too. Your healthcare provider can help you decide which remedies are safe for you to try.

To reduce irritation in the future, it helps to alternate the site of injection with each dose of Nucala. It’s recommended to switch between the outer thigh and stomach. You can also receive the injection in your upper arm with help from a friend or family member.

2. Headache

A headache is the most common Nucala side effect. It’s reported to occur in nearly one-fifth of people prescribed the medication for severe asthma. But during clinical trials, this was only slightly higher than people who didn’t receive Nucala. So it’s possible that the headaches were from inhaled steroids (used in both groups) or from asthma in general.

To manage headaches, OTC pain medications, such as acetaminophen, may help. It may also be beneficial to maintain a daily routine that includes stress-reducing activities, such as deep breathing exercises and spending time outside. Making sure you get enough sleep every night can help lower your risk of getting headaches, too.

If headaches continue or worsen, or you find yourself frequently turning to OTC pain medications for relief, it’s important to let your healthcare provider know. They may be able to suggest other methods to alleviate the pain you’re experiencing. In some cases, they may opt to run tests to see if there’s another reason you’re experiencing headaches.

3. Throat, back, and joint pain

Some people receiving Nucala may develop pain in one or more areas of the body, such as the throat, back, or joints. Throat and joint pain are less common among people receiving Nucala for asthma compared to those using it for other health conditions.

Lozenges, throat sprays, and humidifiers can all be useful for soothing throat pain. And gentle stretching or low-impact physical activity may help address back and joint pain associated with Nucala use. The same goes for heating pads or warm compresses; they can help provide targeted relief to areas of discomfort. OTC pain relievers may help reduce inflammation and ease pain, too.

If pain management methods like these aren’t alleviating your pain, talk to your provider to discuss different options for pain management.

4. Fatigue

Fatigue, or feeling tired, is another possible Nucala side effect. For people whose asthma symptoms aren’t well controlled, fatigue can become an even bigger challenge. Fortunately, there are several approaches you can take to manage fatigue.

While it seems counterintuitive, regular exercise can help boost your energy levels and contribute to restful sleep. Eating nutritious foods and drinking plenty of water is also essential to maintain your energy throughout the day. Certain breathing exercises and meditation have also been found to improve symptoms of fatigue.

If fatigue is interfering with your daily life, it’s important to reach out to your provider. There may be many different reasons you’re experiencing fatigue, and your provider can help you determine if Nucala is the cause of your symptoms.

5. Increased risk of infection

Although it’s not common, Nucala could increase your risk of developing an infection. This is because Nucala weakens the immune system, which is actually how it helps treat conditions like eosinophilic asthma.

Parasitic infections may be more difficult to treat after starting Nucala. Because of this, your healthcare provider will likely check for parasitic infections before you start the medication. If you have a parasitic infection, it must be treated before starting Nucala.

There have also been cases where people receiving Nucala developed herpes zoster (shingles) infections. Ask your healthcare provider whether you should receive the shingles vaccine (Shingrix) before starting Nucala. Other infections reported with Nucala use include influenza (the flu) and urinary tract infections.

When to contact a healthcare provider about Nucala side effects

Serious Nucala side effects are rare. But it’s important to be aware of the symptoms to look out for and know when you should give your healthcare provider a call.

If you notice any signs or symptoms of an infection, it’s time to get in touch with your provider. Treating an infection early on is important to prevent any future complications. Signs and symptoms of an infection include:

• Fever

• Chills

• New or persistent cough

• Sore throat

• Pain or burning when you pee

Difficulty breathing, severe lightheadedness or dizziness, and swelling in the face or throat, are possible symptoms of a serious allergic reaction. If you experience any of these symptoms, you should call 911 or have someone take you to the nearest ER right away.

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Written by:

Vanessa Carranza, PharmD

Vanessa Carranza, PharmD, is a pharmacist who has dedicated her career to the advancement of medical education for healthcare providers, patients, and caregivers, most notably in the oncology space.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

Reviewed by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

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