Mepolizumab

Pronunciation: mep-oh-LIZ-oo-mab.

Generic name
mepolizumab
Drug class
Monoclonal antibody (anti-IL-5, interleukin-5 antagonist)
Form
Pre-filled syringe/pen (40 mg or 100 mg) or powder for reconstitution
Route
Subcutaneous injection
Legal status
Prescription-only, specialist-initiated (respiratory/allergy/rheumatology)

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia

Australia: Nucala (4) · Full directory

What mepolizumab is and how it works

Mepolizumab is a prescription-only injectable biologic that reduces a type of white blood cell called eosinophils, which drive inflammation in several conditions including severe asthma, chronic sinus inflammation with nasal polyps, some cases of COPD, and certain rare inflammatory blood/vessel conditions. (1)

Mepolizumab is given as an injection under the skin, usually every 4 weeks, alongside your other regular treatments for your specific condition -- it is not a rescue medicine and does not treat sudden symptoms.

Mechanism of action: how mepolizumab works

Mepolizumab is a humanised monoclonal antibody that blocks interleukin-5 (IL-5) from binding its receptor on eosinophils, reducing eosinophil production and survival -- addressing the underlying eosinophil-driven inflammation in each approved condition. (1)

What mepolizumab is used for

Severe eosinophilic asthma

Used as an add-on maintenance treatment in patients aged 6 and older with severe asthma driven by high eosinophil levels. (1)

Chronic rhinosinusitis with nasal polyps (CRSwNP)

Used as an add-on maintenance treatment in adults with long-term sinus inflammation and nasal polyps. (1)

COPD with eosinophilia

Used as an add-on maintenance treatment in adults with COPD that isn't adequately controlled and has raised eosinophil levels. (1)

Eosinophilic granulomatosis with polyangiitis (EGPA) and hypereosinophilic syndrome (HES)

Used to treat these rarer conditions involving eosinophil-driven inflammation of blood vessels or other tissues, in adults (EGPA) or patients 12 and older with HES lasting 6 months or more. (1)

Before taking mepolizumab

Do not take / not appropriate for

  • Do not use mepolizumab if you have had a serious allergic reaction to it or any of its ingredients. (all countries) (1)

Tell your clinician about

  • Any current or recent parasitic (worm) infection -- this should be treated before starting.
  • Whether you currently take steroid tablets or inhalers -- these should not be stopped suddenly when starting mepolizumab.
  • Any previous shingles infection, or whether you're up to date with shingles vaccination if appropriate.
  • Pregnancy, plans for pregnancy, or breastfeeding.
(1)

How to take mepolizumab

  • Mepolizumab is given as an injection under the skin (upper arm, thigh, or abdomen), usually every 4 weeks.
  • The exact dose depends on which condition is being treated and, for asthma, your age -- follow your prescriber's specific instructions.
  • It does not replace your regular reliever inhaler or other prescribed treatments.
  • Any reduction in your steroid dose should be gradual and supervised by your clinician, not stopped abruptly.
(1)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4)

Missed dose

If you miss a dose, give it as soon as possible, then resume your usual dosing day going forward.

Overdose

Contact your prescriber or seek medical advice if too much mepolizumab has been given. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Headache, tiredness, and back pain (asthma).

What to notice: Headache, tiredness, and back pain (asthma).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Sore throat and joint pain (CRSwNP).

What to notice: Sore throat and joint pain (CRSwNP).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Diarrhoea and cough (COPD).

What to notice: Diarrhoea and cough (COPD).

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Injection site reactions.

What to notice: Injection site reactions.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Signs of a serious allergic reaction (anaphylaxis) — emergency

Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; wheezing; low blood pressure; widespread rash or hives. This can happen within hours of an injection, but sometimes appears later.

Action: Seek emergency medical help immediately. Your prescriber will decide whether it is safe to continue treatment. (1)

Signs of a parasitic (worm) infection — high caution

Symptoms: Unexplained abdominal pain, diarrhoea, or unusual tiredness.

Action: Tell your prescriber -- any existing parasitic infection should be treated first, and treatment may be paused if an infection develops that doesn't respond to standard treatment. (1)

Signs of shingles (herpes zoster) — high caution

Symptoms: A painful, blistering rash, often in a band on one side of the body.

Action: Tell your prescriber promptly -- shingles vaccination may be considered if appropriate for you. (1)

Interactions

  • No formal drug interaction studies have been performed with mepolizumab, but population data show no evidence of interaction with commonly co-prescribed medicines. Tell your prescriber about everything else you take. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

There is not enough human data to know the exact risk in pregnancy. Antibody medicines like this one cross the placenta, with a greater effect likely later in pregnancy. Animal studies at much higher doses than used in humans did not show harm to the developing baby. Discuss with your prescriber if you are pregnant or planning pregnancy. (1) (2) (3) (4)

Breastfeeding

It is not known whether mepolizumab passes into human breast milk in meaningful amounts. Discuss the benefits and risks with your prescriber. (1) (2) (3) (4)

Children

Approved for severe asthma from age 6, and for hypereosinophilic syndrome from age 12; other indications are for adults only. (1) (2) (3) (4)

Elderly

No specific dose adjustment based on age alone is described in the source reviewed. (1) (2) (3) (4)

Hepatic_impairment

Not established in the source reviewed for this dossier. (1) (2) (3) (4)

Renal_impairment

Not established in the source reviewed for this dossier. (1) (2) (3) (4)

Monitoring

Before starting

  • Screening for pre-existing parasitic infection
  • Eosinophil count where relevant to diagnosis
  • Vaccination status (including shingles, where appropriate)

During treatment

  • Ongoing monitoring for allergic reaction symptoms after each injection.
  • Monitoring of asthma, sinus, COPD, or vasculitis symptoms to assess response.
  • Gradual, supervised reduction of corticosteroids if appropriate.
(1)

Storage

Refrigerate pre-filled devices at 36-46°F (2-8°C), protected from light. May be kept unrefrigerated up to 86°F (30°C) for a maximum of 7 days, and should be used within 8 hours of removal from the carton. Powder vials are stored below 77°F (25°C); reconstituted solution is used within 8 hours. Keep out of the reach of children.

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing information; verify against the current full label before prescribing.

United States

Indication: Severe eosinophilic asthma / CRSwNP / COPD / EGPA / HES

Dose summary: Asthma 12+ years: 100mg SC every 4 weeks; 6-11 years: 40mg SC every 4 weeks. CRSwNP/COPD: 100mg every 4 weeks. EGPA/HES: 300mg every 4 weeks as three 100mg injections >=5cm apart. Not for acute bronchospasm/exacerbations. Treat pre-existing helminth infection before initiation.

Renal context: Not established in the source reviewed for this dossier. (1)

Mechanism of action

Hepatic guidance

Not established in the source reviewed for this dossier.

Overdose note

No specific antidote described in the source reviewed; manage supportively and seek prescriber guidance for suspected overdose. (1)

Frequently asked questions

Is mepolizumab (Nucala) available in the US, UK, Europe, Canada, and Australia?

Yes, it is approved in all of these regions, though the exact approved conditions can differ slightly by country. New Zealand-specific approval was not found in this research and should be confirmed locally. (1) (2) (3) (4)

Does the dose stay the same for every condition mepolizumab treats?

No. The dose depends on which condition is being treated -- most conditions use 100 mg every 4 weeks, younger children with asthma use 40 mg, and the rarer conditions EGPA and HES use a higher 300 mg dose given as three separate injections. (1)

Can I stop my other asthma or COPD medicines once I start mepolizumab?

No, not on your own. Mepolizumab is an add-on maintenance treatment, not a replacement for your inhaled or oral corticosteroids. Reducing or stopping other corticosteroid treatment must be done gradually and only under your prescriber's supervision, since stopping abruptly can be unsafe. (1)

What is the mechanism of action of mepolizumab?

Mepolizumab is a humanised monoclonal antibody that blocks interleukin-5 (IL-5) from binding its receptor on eosinophils, reducing eosinophil production and survival -- addressing the underlying eosinophil-driven inflammation in each approved condition. (1)

What is the generic name of Mepolizumab?

The generic name is mepolizumab. (1)

What class of drug is mepolizumab?

Mepolizumab is classed as: Monoclonal antibody (anti-IL-5, interleukin-5 antagonist). (1)

References

  1. NUCALA (mepolizumab) -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information, GlaxoSmithKline LLC · United States · accessed 2026-07-29 · source 1
  2. European Commission approval history for Nucala (mepolizumab)GSK corporate press releases · European Union · accessed 2026-07-29 · source 2
  3. MHRA and Health Canada approvals for Nucala (mepolizumab)Pearce IP legal/regulatory news summary and GSK press releases · United Kingdom / Canada · accessed 2026-07-29 · source 3
  4. NUCALA -- ARTG registrationTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-29 · source 4

Brand names by country

Single-ingredient mepolizumab names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Nucala100 mg/mL, 40 mg/.4mL · glaxosmithkline llc

United Kingdom

  • Nucala (3)MHRA approved confirmed · 100 mg · GlaxoSmithKline UK Limited

Canada

  • NUCALA

Australia

  • Nucala (4)TGA ARTG registered 2016-02-02 · 100 mg · GlaxoSmithKline Australia Pty Ltd
View brands in additional countries.

European Union

Nucala (2)