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Nucala: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Oct 12, 2022.

1. How it works

  • Nucala is a brand (trade) name for mepolizumab which is a biologic that may be used to reduce high numbers of eosinophils.
  • Nucala (mepolizumab) works by binding to interleukin 5 (IL-5 or IgG1 kappa) which is the main cytokine responsible for the growth and differentiation, recruitment, activation, and survival of eosinophils. Cytokines are small secreted proteins that are involved in cell signaling and interactions. Mepolizumab binds to IL-5 and prevents it from binding to the Il-5 receptor complex on the surface of eosinophils. This reduces the production and survival of eosinophils. Eosinophils are one of multiple cell types and mediators that are involved in inflammation, and inflammation is an important component in the pathogenesis of asthma, EGPA, and HES. The exact way mepolizumab works in asthma, EGPA, and HES has not been definitively established.
  • Nucala belongs to the class of medicines known as interleukin inhibitors.

2. Upsides

  • May be used as an add-on maintenance treatment for severe eosinophilic asthma in adults and children aged 6 and older. This is a subtype of asthma that is characterized by high numbers of eosinophils in the blood. Eosinophils are a type of white blood cell and this type of asthma affects 5% of all asthmatics.
  • Also approved for the treatment of adult patients with eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome) and the treatment of patients ≥12 years with hypereosinophilic syndrome (HES).
  • May be used as an add-on maintenance treatment of chronic rhinosinusitis with nasal polyps (CRSwNP) in adults aged 18 years of age and older with inadequate response to nasal corticosteroids.
  • Administered once every four weeks by subcutaneous injection. The usual dosage for severe eosinophilic asthma is 100mg every 4 weeks for adults and children aged at least 12 years and 40mg every 4 weeks for children aged 6 to 11 years. For eosinophilic granulomatosis with polyangiitis and hypereosinophilic syndrome, the usual dosage is 300mg every 4 weeks.
  • Available as a single-use prefilled syringe and autoinjector (an automatic injection).
  • People can be taught how to self-administer Nucala. 99% of people can successfully self-administer the Nucala prefilled syringe and 89-95% can successfully administer the Nucala autoinjector.
  • Effective in both adults and children at reducing blood eosinophil counts. After 4 weeks, blood eosinophils were reduced by an average of 84% in adults and 85% in children aged 6 to 11 years.
  • Weight gain is not reported as a side effect of Nucala in the product information. However, anecdotally, some people have reported a small amount of weight gain on blog sites, although equally as many people report weight loss as well, usually because they no longer need to take as much prednisone.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Headaches, injection site reactions (redness, pain, itching, or swelling at the injection site), back pain, and tiredness are the most common side effects reported with Nucala. Urinary tract infections, the flu, stomach pain, itch, eczema, and muscle spasms may also be reported. Rarely, allergic reactions may occur and it may precipitate shingles.
  • Must be given by subcutaneous injection, although people can be taught how to self-administer.
  • Nucala will not treat an asthma attack or exacerbations of asthma (acute bronchospasm or status asthmaticus).
  • Serious hypersensitivity reactions (such as angioedema and urticaria) have been reported in people administered Nucala, usually within hours of administration but sometimes days later. A health professional should always administer the first dose of Nucala and patients should be advised to seek urgent emergency help if they experience an allergic-type reaction.
  • Nucala may precipitate herpes zoster. Consider vaccination if medically appropriate.
  • People prescribed Nucala may not require the same dosages of systemic or inhaled corticosteroids (ICS). However, these should not be discontinued abruptly. Instead, reductions should be gradual and performed under the direct supervision of a physician. Be aware that corticosteroid dosage reductions may be associated with withdrawal symptoms or unmask conditions previously suppressed by corticosteroid therapy.
  • Nucala may influence a person's response to parasitic infections (such as threadworm) because eosinophils may be involved in the immunological response to these infections. Treat any existing parasitic infections before starting Nucala. If patients become infected during treatment with Nucala and do not respond to anti-helminth treatments, discontinue Nucala until the infection resolves.
  • A small percentage of people receiving Nucala may develop antibodies to it, which may slightly increase its clearance. The clinical relevance of this is not known as there has been no evidence of a correlation between anti-mepolizumab antibody titers and a change in eosinophil level.
  • It is unknown what effect Nucala has during pregnancy on the unborn child. There are no data on the effect of Nucala during lactation. The risks vs benefits need to be weighed up. Any woman that does become pregnant while being administered Nucala should enroll on the pregnancy exposure registry by calling 1-877-311-8972 or visiting

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Nucala is a biologic that works by blocking the action of IL-5 which is the main cytokine responsible for the survival and production of eosinophils. Nucala may be used to treat severe eosinophilic asthma, eosinophilic granulomatosis with polyangiitis, hypereosinophilic syndrome, and chronic rhinosinusitis with nasal polyps. Common side effects include a headache and injection site reactions and it may increase the risk of herpes zoster infections.

5. Tips

  • Nucala is usually given once a month. Initially, your doctor will administer it, but during your appointment, they will discuss teaching you how to administer it so that you can administer it at home. This will save you from going to your doctor once a month.
  • If you don’t like needles, ask for the Nucala autoinjector because it can be administered without seeing the needle.
  • Both the Nucala prefilled syringe and autoinjector need to be stored in the refrigerator at 36°F to 46°F (2°C to 8°C). Keep them in their original carton to protect them from light. Do not freeze. Do not shake. Avoid exposure to heat. Before using, take one Nucala syringe or autoinjector (whatever you have been prescribed) out of the refrigerator, and leave it to warm up to room temperature for at least 30 minutes (but no longer than eight hours). Do not heat it in direct sunlight, the microwave, or in hot water because this will ruin the medicine. A Nucala injection may be stored in its original carton outside the refrigerator at up to 86°F (30°C) for up to 7 days. But it should be discarded if not used within this time and should not be put back into the refrigerator. If removed from its carton Nucala injection must be administered within 8 hours.
  • Do not use the medicine if it is cloudy, has particles in it, or is passed its expiry date. The medicine should look clear to pale yellow or pale brown. It is normal for one or more air bubbles to be present.
  • Only inject into clear, healthy skin. Do not inject into any areas that are bruised, tender, red, scaly, or hard. You should also not inject into any scars, stretch marks, or areas of eczema.
  • Nucala can be self-injected into the thighs or abdomen. If you are a caregiver administering Nucala to another person, it may also be administered into the upper arm. If you require 2 injections at a time, separate the administration sites by at least 2 inches. Wash your hands and clean the injection site with an alcohol swab.
  • For the prefilled syringe, first, pull off the gray needle cap. Use your free hand to pinch the skin up around your injection site and insert the entire needle at a 45° angle into the pinched skin. Move your thumb to the white plunger and slowly push down on the plunger to inject your full dose. Make sure the plunger is completely down. Once your injection is complete, lift your thumb off the plunger and this will automatically make the needle retract out of your skin. There may be a small drop of blood at the injection site but this is normal. Do not rub your injection site. Do not put the clear cap back on the syringe. Throw the syringe away in an FDA-cleared sharps disposal container or another suitable sharps container.
  • To administer the Nucala autoinjector first remove the clear needle cap from the end of the autoinjector by pulling it off. Do not touch the yellow needle guard on the end because this may set off the injection prematurely. Hold the autoinjector straight up and down (at a 90° angle) onto your preferred injection site. To start the injection push the autoinjector all the way down while holding it against your skin. You should hear a click to let you know the injection has started. Your injection may take up to 15 seconds to complete. Continue to hold it down until you hear a second click and the inspection window is filled with the yellow indicator. After you hear the second click, continue to hold it down for 5 more seconds. Remove the autoinjector. There may be a small drop of blood at the injection site but this is normal. Do not rub your injection site. Do not put the clear cap back on the autoinjector. Throw the autoinjector away in an FDA-cleared sharps disposal container or another suitable sharps container.
  • If you think you are gaining weight on Nucala, keep a diary that documents your daily diet, amount of exercise, and daily weight gain. Try to eat a healthy diet and exercise regularly. If there is a clear pattern of weight gain, talk with your doctor.
  • Seek urgent medical attention if you experience shortness of breath, or facial or throat tightness after administering Nucala. If you feel unwell, or experience other signs of infection, tell your doctor immediately. Also remember to tell your doctor about any other side effects that you may be experiencing, such as headache or back pain.
  • Nucala does not treat an asthma attack or worsening asthma. Seek medical advice if your asthma remains uncontrolled or worsens after initiation of treatment with Nucala.
  • If you have a parasitic infection, it should be treated before you start Nucala.
  • Tell other health professionals that you are being administered Nucala. Nucala may increase your risk of herpes infection. If you are at high risk, your doctor may consider vaccination against herpes.
  • It is unknown what effect Nucala has on an unborn baby. Tell your doctor immediately if you become pregnant while being administered Nucala and enroll in the Pregnancy Exposure Registry by calling 1-877-311-8972 or by visiting
  • Talk to your doctor or pharmacist before taking any other medicines with Nucala. Do not change any other medications, such as reducing your corticosteroid dosage, without talking to your doctor first.

6. Response and effectiveness

  • Nucala starts working within 48 hours; however, it may take up to 4 weeks before the maximum effect of Nucala is seen for both asthma and eosinophilic granulomatosis with polyangiitis (EGPA).
  • In trials of people with eosinophilic asthma, reductions in blood eosinophils were seen within 48 hours of a dose of mepolizumab for all treatment doses. Greater eosinophil reductions were seen with higher mepolizumab dosages, for example, 64% with a 12.5mg SC dose, 78% for a 75mg dose, and 90% with a 250mg SC dose.
  • After treatment with Nucala 100mg SC every 4 weeks, blood eosinophils showed an average reduction of 84% (down to 40 cells/mcL) in adults.
  • After treatment with Nucala 40mg SC every 4 weeks, blood eosinophils showed an average reduction of 85% (down to 48 cells/mcL) in children aged 6 to 11 years.
  • The greatest effect was seen after 4 weeks of treatment and this was maintained throughout the treatment period.
  • In trials of people with EGPA blood eosinophil levels were reduced by 83% (down to 38 cells/mcL) with mepolizumab 300mg every 4 weeks.

7. Interactions

There have been no formal interaction studies conducted with Nucala according to the product information, and no interactions are documented.

You should refer to the prescribing information for Nucala for any updates or newly noted interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Nucala only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2023 Revision date: October 12, 2022.