Prescription medication · Anti-IL-5 Monoclonal Antibody
mepolizumab
Also sold as Nucala. 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).
Data updated 2026-05-15
- 47,215
- FDA reportsOften reported
- Rx
- Availability
mepolizumab (Nucala) is a prescription Anti-IL-5 Monoclonal Antibody. 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).
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.
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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.
The sections below are summarized in plain English from mepolizumab's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
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.
This is a plain-language summary of mepolizumab's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
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.
This is a plain-language summary of mepolizumab's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose of Nucala, call your doctor right away to reschedule your injection. Do not double your next dose.
This is a plain-language summary of mepolizumab's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store Nucala in the refrigerator, protected from light, and do not freeze.
Side Effects (from patient reports)
Based on 47,215 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for mepolizumab, by number of reports
- Asthma
Asthma
12,416 reports
- Shortness of breath
Shortness of breath
10,201 reports
- Wheezing
Wheezing
6,904 reports
- Cough 4,939
Cough
4,939 reports
- Treatment not fully effective 4,917
Treatment not fully effective
4,917 reports
- Pneumonia 4,419
Pneumonia
4,419 reports
- Difficulty with daily activities 4,148
Difficulty with daily activities
4,148 reports
- Sleep problems due to a medical condition 3,042
Sleep problems due to a medical condition
3,042 reports
- Tiredness 2,918
Tiredness
2,918 reports
- Feeling unwell 2,633
Feeling unwell
2,633 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for mepolizumab each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where mepolizumab sits
mepolizumab has more FDA adverse-event reports than 72% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is mepolizumab; the line is the median (50th percentile).
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
Reports Mentioning Death
3,552
7.5% of reports — not proof of cause
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 |
| 5 | COUGH | 4,939 |
| 6 | THERAPEUTIC PRODUCT EFFECT INCOMPLETE | 4,917 |
| 7 | PNEUMONIA | 4,419 |
| 9 | LOSS OF PERSONAL INDEPENDENCE IN DAILY ACTIVITIES | 4,148 |
| 10 | SLEEP DISORDER DUE TO A GENERAL MEDICAL CONDITION | 3,042 |
| 12 | FATIGUE | 2,918 |
| 13 | MALAISE | 2,633 |
| 14 | CONDITION AGGRAVATED | 2,605 |
| 15 | HEADACHE | 2,524 |
| 16 | PAIN | 2,339 |
| 17 | PRODUCTIVE COUGH | 2,235 |
| 18 | NASOPHARYNGITIS | 2,117 |
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 47,215 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.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
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