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.
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
- Dyspnoea
Dyspnoea
10,201 reports
- Wheezing
Wheezing
6,904 reports
- Cough 4,939
Cough
4,939 reports
- Therapeutic Product Effect Incomplete 4,917
Therapeutic Product Effect Incomplete
4,917 reports
- Pneumonia 4,419
Pneumonia
4,419 reports
- Loss Of Personal Independence In Daily Activities 4,148
Loss Of Personal Independence In Daily Activities
4,148 reports
- Sleep Disorder Due To A General Medical Condition 3,042
Sleep Disorder Due To A General Medical Condition
3,042 reports
- Fatigue 2,918
Fatigue
2,918 reports
- Malaise 2,633
Malaise
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) 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?
What pregnancy or breastfeeding source fields are listed for mepolizumab?
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Compare beyond drug class
Nationwide peers by FAERS volume & death-report share
Two PlainMeds-derived comparison paths for mepolizumab: nearest FDA FAERS report volume and nearest death-report share among drugs with at least 1,000 logged reports, excluding same-class neighbors listed above. Counts reflect reporting volume, not proven individual harm.
Similar FAERS report volume
Nearest drugs by total FAERS reports. This record: 47,215.
Similar death-report share
Nearest drugs by FAERS death-report share. This record: 7.52%.
- amitriptyline Δ 0.01 pts · 16,403 reports · Tricyclic Antidepressant (TCA) 7.53%death share
- ivabradine Δ 0.03 pts · 6,539 reports · HCN Channel Blocker 7.55%death share
- irbesartan Δ 0.04 pts · 43,004 reports · Angiotensin II Receptor Blocker (ARB) 7.48%death share
- baclofen Δ 0.08 pts · 83,476 reports · GABA-B Agonist (Muscle Relaxant) 7.44%death share
Medication Guides
Understanding Drug Interactions
How CYP450 enzymes, inhibitors, and inducers affect your medications
Generic vs Brand Name Drugs
FDA requirements, cost savings, and when the difference matters
Narrow Therapeutic Index Drugs
FDA bioequivalence and label-record context for narrow therapeutic index medicines
Common Drug Interactions
Dangerous medication combinations and how to protect yourself
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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 are separate source-record fields. This page is a public FDA/CMS registry and does not provide medical, treatment, substitution, or medication-change directions.
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. This registry does not provide medication decisions.
Last updated: August 6, 2025
PlainMeds is rendered directly from FDA openFDA/FAERS extracts, DailyMed labels, and CMS drug-pricing files, no number is typed in by an editor. FAERS counts, recalls, shortages, and price figures on this page are queried live from those federal extracts. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-05-15. Primary sources: openFDA / FAERS, DailyMed and CMS Part B ASP.
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 from the source snapshot dated . See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a data issue.
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