Pharmacologic class (EPC) · 3 drug pages

Interleukin-5 antagonist: adverse event reports filed with FDA

47,270 reports list a drug in this class as a suspect or interacting product, 2013–2026.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

47,270
reports across the class: 0.2% of all reports; 5,022
reports, 12 months to June 2026: 7,355 in the 12 months before; 62.7%
marked serious by the reporter: 57.4% across all reports; 3
drugs with a page: brand and generic names counted separately

Interleukin-5 antagonist is a pharmacologic class (an FDA Established Pharmacologic Class) with 3 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 47,270 adverse event reports received by FDA, 0.2% of the database, from August 2013 to June 2026.

5,022 reports arrived in the 12 months to June 2026, down 32% from 7,355 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 62.7% of the class's reports are marked serious, 8.1% record death among the outcomes and 32.5% record hospitalisation, as reported.

Across the class the reactions recorded most often are asthma (25.5%), dyspnoea (21.4%) and wheezing (14.4%). The class median share shown beside each term is the middle value across the member drugs; it is the comparison used on every drug page in this class.

The members table is ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Drugs in the class

Drug	Name type	Reports	Latest 12 months	Marked serious	Top term recorded
NucalaMepolizumab	brand	30,572	4,066	44.5%	Asthma
Mepolizumab	generic	16,162	906	97.2%	Asthma
CinqairReslizumab	brand	536	50	58.4%	Incorrect dose administered

Ordered by report count for navigation only. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."

Reports by month, five years

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Reactions recorded across the class

share of class reports recording the termmedian drug in the class

Asthmaasthma25.5%12,033
Dyspnoeashortness of breath21.4%10,130
Wheezingwheezing14.4%6,787
Product dose omission issuea dose was missed14.1%6,660
Coughcough10.5%4,970
Pneumonialung infection9.7%4,574
Therapeutic product effect incomplete9.6%4,549
Drug ineffectivethe medicine did not work as expected9.1%4,302
Loss of personal independence in daily activities8.4%3,960
Fatiguetiredness6.3%2,984
Off label useused for a purpose or in a way not on the label6.2%2,939
Sleep disorder due to a general medical condition6.1%2,870
Malaisegeneral feeling of being unwell5.8%2,763
Condition aggravatedthe condition being treated got worse5.5%2,614
Headachehead pain5.5%2,582
Painpain, site not specified5.1%2,402
Productive cougha cough with phlegm4.7%2,224
Nasopharyngitisa cold4.5%2,106
Obstructive airways disorder4.4%2,097
Hospitalisationadmission to hospital4.1%1,955
Chest discomfortchest discomfort4%1,912
Inappropriate schedule of product administrationthe product was taken at the wrong times3.9%1,848
Arthralgiajoint pain3.8%1,802
Full blood count abnormal3.7%1,753
Rashskin rash3.6%1,725

Solid bar: share of all class reports. Hollow bar: the median share across the 3 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death8.1%3,827

Life-threatening4.4%2,070

Hospitalisation (initial or prolonged)32.5%15,358

Disability3.5%1,658

Congenital anomaly3.4%1,592

Other serious48.3%22,817

Not serious37.3%17,634

Patient age

Under 20.1%28

2 to 110.2%94

12 to 170.3%140

18 to 447.8%3,707

45 to 6416%7,581

65 to 7410.5%4,941

75 and over6.7%3,179

Age not given58.4%27,600

Who reported

Physician15.8%7,479

Pharmacist2.8%1,339

Other health professional19.3%9,132

Lawyer0%1

Consumer or non-health professional61.1%28,860

Not given1%459

Grey bar: all 20,646,523 reports in the database. Outcome flags are as the reporter set them and are not verified by FDA.

Questions about Interleukin-5 antagonist reports

Which drugs are in the Interleukin-5 antagonist class on this site?

Nucala, Mepolizumab and Cinqair. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

47,270 reports through June 2026, 5,022 of them in the latest 12 months. A report listing two drugs of the class counts once for each.

What reactions are recorded most often?

asthma (25.5%), dyspnoea (21.4%), wheezing (14.4%), product dose omission issue (14.1%) and cough (10.5%).

Can the members table be used to rank the drugs?

No. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic." Drugs differ in how many people take them, in the conditions they treat, in time on the market and in how diligently reports are collected.

How do I report an adverse event?

Through FDA MedWatch (Form FDA 3500, or 1-800-FDA-1088) or to the manufacturer. See the guide on how to report.

Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A class is the Established Pharmacologic Class most often attached to a drug's reports by openFDA's label harmonisation, or from the NDC Directory where reports carry none. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.

Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.