mepolizumab
Brand names: Nucala
Nucala is a medicine that can help control certain types of asthma and other conditions. It works by blocking a protein in your body that causes inflammation.
What it does
Nucala is used as an add-on treatment for severe asthma in adults and kids 6 years and older when their asthma is not well controlled and they have high levels of eosinophils (a type of white blood cell).
Common side effects
Headache, Injection site reaction (pain, redness, swelling), Back pain
Key warnings
Nucala can cause serious allergic reactions, including anaphylaxis.
How It Works
Nucala is a monoclonal antibody that targets interleukin-5 (IL-5). IL-5 is a protein that helps eosinophils grow and survive. By blocking IL-5, Nucala lowers the number of eosinophils in your blood and lungs, which can reduce inflammation and improve your symptoms.
How to Take It
Nucala is given as a shot under the skin (subcutaneous injection) every 4 weeks. The dose depends on your condition and age. For asthma, adults and kids 12+ get 100 mg, and kids 6-11 get 40 mg. For EGPA and HES, the dose is 300 mg, given as three separate 100 mg injections.
Pregnancy & Breastfeeding
It is not known if Nucala will harm your unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is also not known if Nucala passes into breast milk, so talk to your doctor about breastfeeding while taking Nucala.
Missed Dose
If you miss a dose of Nucala, call your doctor right away to reschedule your injection. Do not double your next dose.
Storage
Store Nucala in the refrigerator, protected from light, and do not freeze.
Side Effects (from patient reports)
Based on 61,585 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 47,215 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2008–2025.
Total Reports
47,215
Death-Related Reports
3,552
Hospitalization Reports
15,164
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | ASTHMA | 12,416 |
| 2 | DYSPNOEA | 10,201 |
| 3 | WHEEZING | 6,904 |
| 4 | PRODUCT DOSE OMISSION ISSUE | 6,194 |
| 5 | COUGH | 4,939 |
| 6 | THERAPEUTIC PRODUCT EFFECT INCOMPLETE | 4,917 |
| 7 | PNEUMONIA | 4,419 |
| 8 | DRUG INEFFECTIVE | 4,405 |
| 9 | LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES | 4,148 |
| 10 | SLEEP DISORDER DUE TO A GENERAL MEDICAL CONDITION | 3,042 |
| 11 | OFF LABEL USE | 2,930 |
| 12 | FATIGUE | 2,918 |
| 13 | MALAISE | 2,633 |
| 14 | CONDITION AGGRAVATED | 2,605 |
| 15 | HEADACHE | 2,524 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Nucala can cause serious allergic reactions, including anaphylaxis. Get medical help right away if you have signs of an allergic reaction like hives, swelling, or trouble breathing. You may get herpes zoster (shingles) while taking Nucala, so consider getting vaccinated. Do not stop taking steroid medicines suddenly when you start Nucala. Talk to your doctor about slowly reducing your steroid dose.
Common Questions
What if I have a parasitic infection?
Can Nucala be used for sudden asthma attacks?
How will I know if Nucala is working?
Can I stop taking my other asthma medicines?
Where on my body can I get the injection?
Will I administer the injection myself?
What should I do if I think I'm having an allergic reaction to Nucala?
Can Nucala cure my asthma?
How long will I need to take Nucala?
What ingredients are in Nucala?
What are the common side effects of mepolizumab?
What drug class is mepolizumab?
Is mepolizumab safe during pregnancy?
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What the FDA Data Shows for mepolizumab
The FDA label for mepolizumab (sold under brand names such as Nucala) classifies it as a prescription-only medication in the Anti-IL-5 Monoclonal Antibody class. Nucala is used as an add-on treatment for severe asthma in adults and kids 6 years and older when their asthma is not well controlled and they have high levels of eosinophils (a type of white blood cell). Official labeling lists 8 commonly reported side effects, including Headache, Injection site reaction (pain, redness, swelling), Back pain.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 61,585 voluntary reports. Interaction data is drawn directly from FDA-approved prescribing information. Acquisition-cost data is surveyed weekly by CMS and updated as manufacturers report changes.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: August 6, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages