Pharmacologic class (EPC) · 6 drug pages

Aromatase inhibitor: adverse event reports filed with FDA

70,406 reports list a drug in this class as a suspect or interacting product, 2004–2026.

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.

70,406
reports across the class: 0.3% of all reports; 4,804
reports, 12 months to June 2026: 4,596 in the 12 months before; 82.2%
marked serious by the reporter: 57.4% across all reports; 6
drugs with a page: brand and generic names counted separately

Aromatase inhibitor is a pharmacologic class (an FDA Established Pharmacologic Class) with 6 drug pages on this site. Together those drugs are listed as a suspect or interacting product in 70,406 adverse event reports received by FDA, 0.3% of the database, from January 2004 to June 2026.

4,804 reports arrived in the 12 months to June 2026, close to the 4,596 of the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. 82.2% of the class's reports are marked serious, 9.4% record death among the outcomes and 24% record hospitalisation, as reported.

Across the class the reactions recorded most often are fatigue (10.1%), arthralgia (9.5%) and malignant neoplasm progression (8.6%). 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
Letrozole	generic	27,849	2,523	89.9%	Neutropenia
ArimidexAnastrozole	brand	10,217	95	58%	Arthralgia
Anastrozole	generic	10,122	1,234	86.4%	Arthralgia
FemaraLetrozole	brand	8,770	367	89.1%	Fatigue
Exemestane	generic	7,041	473	85.5%	Malignant neoplasm progression
AromasinExemestane	brand	6,407	112	67.6%	Arthralgia

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

Fatiguetiredness10.1%7,113
Arthralgiajoint pain9.5%6,698
Malignant neoplasm progression8.6%6,058
Nauseafeeling sick8.2%5,748
Neutropenialow neutrophils, a type of white blood cell6.9%4,829
Diarrhoealoose or frequent stools6.6%4,626
Dyspnoeashortness of breath4.9%3,484
Astheniaweakness or lack of energy4.9%3,452
Headachehead pain4.7%3,315
Metastases to bone4.6%3,230
Painpain, site not specified4.5%3,178
Vomitingbeing sick4.4%3,065
Alopeciahair loss4.2%2,971
Malaisegeneral feeling of being unwell4%2,846
Dizzinesslight-headedness or unsteadiness4%2,807
Hot flusha hot flush3.9%2,764
Breast cancer metastatic3.8%2,688
Breast cancerbreast cancer3.7%2,631
Disease progressionthe disease advanced3.6%2,569
Coughcough3.6%2,552
Decreased appetitereduced appetite3.6%2,530
Insomniadifficulty sleeping3.5%2,444
Pain in extremitypain in an arm or leg3.4%2,414
Metastases to liver3.4%2,371
Myalgiamuscle pain3.3%2,352

Solid bar: share of all class reports. Hollow bar: the median share across the 6 member drugs, the reference used on each member's page. One report can record several terms.

Outcomes, patients and reporters

Outcomes recorded

Death9.4%6,598

Life-threatening3.7%2,580

Hospitalisation (initial or prolonged)24%16,904

Disability2.7%1,913

Congenital anomaly0.2%169

Other serious62.9%44,282

Not serious17.8%12,540

Patient age

Under 20.1%50

2 to 110.1%61

12 to 170.2%127

18 to 445%3,514

45 to 6427.6%19,403

65 to 7418%12,697

75 and over12.8%9,028

Age not given36.3%25,526

Who reported

Physician36%25,314

Pharmacist5.2%3,681

Other health professional21.7%15,259

Lawyer0.1%44

Consumer or non-health professional31.6%22,223

Not given5.5%3,885

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 Aromatase inhibitor reports

Which drugs are in the Aromatase inhibitor class on this site?

Letrozole, Arimidex, Anastrozole, Femara, Exemestane and Aromasin. Class membership comes from the pharmacologic class (EPC) on the drug's FDA label.

How many reports does the class have?

70,406 reports through June 2026, 4,804 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?

fatigue (10.1%), arthralgia (9.5%), malignant neoplasm progression (8.6%), nausea (8.2%) and neutropenia (6.9%).

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.