Antimetabolite adverse event reports that FDA received for the drugs of this class
- Kind of class
- Pharmacologic class (FDA Established Pharmacologic Class)
- Drug pages
- 3
What a report is
A report is not proof that the drug was the cause of the event.
FDA says:
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.
Source: openFDA, Drug Adverse Event Overview, section "Responsible use of the data". The site read the page on . The data have the reports that FDA received through .
FDA also says:
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 has not been scientifically or otherwise verified as to a cause and effect relationship and cannot be used to estimate the incidence of these events.
Source: openFDA, Drug Adverse Event Overview. The site read the page on .
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.
Source: openFDA, Response of the drug event API (meta.disclaimer). The site read the page on .
Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.
Reports on file
Antimetabolite is a pharmacologic class: an FDA Established Pharmacologic Class. The class has 3 drug pages on this site.
From January 2004 to June 2026, FDA received 8,764 adverse event reports that name a drug of the class. In these reports the drug is a suspect or interacting product. A report that names two drugs of the class counts one time for each.
FDA received 431 reports in the 12 months to June 2026 and 644 in the 12 months before. FDA releases FAERS data every quarter, so the newest months are not complete. They grow in later releases.
Of the 1,332,454 drug reports that FDA received in the 12 months to June 2026, 431 (under 0.1%) name a drug of the class. Reports from consumers or other non-health professionals were 20.3% of the reports that name a drug of the class and 45.8% of all drug reports.
The number of people who use the product is not in the data. A count is not a rate.
Pharmacologic class
The Established Pharmacologic Class (EPC) of FDA is the class on the label of a drug. The site puts a drug in the class that its reports have most often.
Data version
openFDA FAERS release of 29 Oct 2026. Reports received through 30 Jun 2026.
Drugs of the class
The rows are in order of name. A brand name and its generic name are separate rows, because reporters name them separately.
FDA says:
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.
Source: openFDA, Drug Adverse Event Overview. The site read the page on .
Importantly, the AEMS data by themselves are not an indicator of the safety profile of the drug or biologic.
Source: FDA, FDA Adverse Event Monitoring System (AEMS) Public Dashboard. Content current as of . The site read the page on .
| Drug | Name type | Reports | Reports, 12 months to June 2026 |
|---|---|---|---|
| HydreaHydroxyurea | Brand name | 2,669 | 38 |
| Hydroxyurea | Generic name | 4,260 | 326 |
| Thioguanine | Generic name | 1,835 | 67 |
Reaction lookup
These are the reaction terms that the reports of the class record. Type a term or a plain word to find its count.
What this list leaves out
The table lists the 738 reaction terms that 5 or more reports record. A term with fewer than 5 reports is not in the table.
The site keeps reaction terms for 8,731 of the 8,764 reports (99.6%).
The reports of the other years are not in the counts.
So a count in the table can be lower than the count of FDA.
The table shows the first 50 of 738 terms.
| Reaction term (MedDRA) and plain meaning | Reports | Share of the 8,764 reports |
|---|---|---|
| Febrile neutropeniafever with low white blood cells | 706 | 8.1% |
| Off label useused for a purpose or in a way not on the label | 615 | 7% |
| Pyrexiafever | 444 | 5.1% |
| Anaemialow red blood cells | 420 | 4.8% |
| Drug ineffectivethe medicine did not work as expected | 416 | 4.7% |
| Thrombocytopenialow platelets | 371 | 4.2% |
| Fatiguetiredness | 329 | 3.8% |
| Nauseafeeling sick | 312 | 3.6% |
| Diarrhoealoose or frequent stools | 274 | 3.1% |
| Neutropenialow neutrophils, a type of white blood cell | 260 | 3% |
| Pancytopenialow counts of all blood cells | 249 | 2.8% |
| Platelet count decreasedlow platelet count | 242 | 2.8% |
| Vomitingbeing sick | 236 | 2.7% |
| Headachehead pain | 229 | 2.6% |
| Pneumonialung infection | 228 | 2.6% |
| Skin ulceran open sore on the skin | 221 | 2.5% |
| Deaththe patient died; cause not stated by this term | 213 | 2.4% |
| Dyspnoeashortness of breath | 213 | 2.4% |
| Astheniaweakness or lack of energy | 206 | 2.4% |
| Haemoglobin decreasedlow haemoglobin | 206 | 2.4% |
| Platelet count increased | 197 | 2.2% |
| Intentional product use issuedeliberate use not as intended | 186 | 2.1% |
| Product use in unapproved indicationused for a purpose not on the label | 181 | 2.1% |
| Painpain, site not specified | 177 | 2% |
| White blood cell count decreasedlow white cell count | 166 | 1.9% |
| Sepsisa severe body-wide response to infection | 162 | 1.8% |
| Abdominal painstomach or belly pain | 153 | 1.7% |
| Haematotoxicity | 149 | 1.7% |
| Splenomegaly | 145 | 1.7% |
| Dizzinesslight-headedness or unsteadiness | 139 | 1.6% |
| White blood cell count increased | 133 | 1.5% |
| Malaisegeneral feeling of being unwell | 128 | 1.5% |
| Acute kidney injurysudden loss of kidney function | 127 | 1.4% |
| Decreased appetitereduced appetite | 125 | 1.4% |
| Cough | 124 | 1.4% |
| Rashskin rash | 123 | 1.4% |
| Weight decreasedweight loss | 123 | 1.4% |
| Pruritusitching | 122 | 1.4% |
| Acute myeloid leukaemia | 121 | 1.4% |
| Falla fall | 120 | 1.4% |
| Mucosal inflammation | 117 | 1.3% |
| Malignant neoplasm progression | 115 | 1.3% |
| Pleural effusionfluid around the lung | 112 | 1.3% |
| Drug intolerancethe medicine was not tolerated | 105 | 1.2% |
| Pain in extremitypain in an arm or leg | 101 | 1.2% |
| Condition aggravatedthe condition being treated got worse | 100 | 1.1% |
| Weight increasedweight gain | 100 | 1.1% |
| Arthralgiajoint pain | 97 | 1.1% |
| Disease progressionthe disease advanced | 97 | 1.1% |
| Interstitial lung diseasescarring or inflammation of lung tissue | 95 | 1.1% |
The counts add to more than 8,764 reports, because one report can record more than one term. FDA says:
No individual drug is connected to any individual reaction. When a report lists multiple drugs and multiple reactions, there is no way to conclude from the data therein that a given drug is responsible for a given reaction.
Source: openFDA, Drug Adverse Event Overview. The site read the page on .
Reports by month
FDA releases FAERS data every quarter, so the newest months are not complete. They grow in later releases.
Outcomes, patients and reporters
| Outcome | Reports | Share | Share as a bar |
|---|---|---|---|
| Death | 1,216 | 13.9% | |
| Life-threatening | 591 | 6.7% | |
| Hospitalization (initial or prolonged) | 3,454 | 39.4% | |
| Disability or Permanent Damage | 151 | 1.7% | |
| Congenital Anomaly/Birth Defect | 54 | 0.6% | |
| Other Serious (Important Medical Events) | 5,445 | 62.1% | |
| Not serious | 919 | 10.5% |
An outcome in a report is not proof that a drug was the cause. The reporter gives the outcome, and FDA does not verify it. A report can have more than one outcome. FDA says:
The information in these reports has not been scientifically or otherwise verified as to a cause and effect relationship and cannot be used to estimate the incidence of these events.
Source: openFDA, Drug Adverse Event Overview. The site read the page on .
| Age | Reports | Share | Share as a bar |
|---|---|---|---|
| Under 2 | 82 | 0.9% | |
| 2 to 11 | 662 | 7.6% | |
| 12 to 17 | 484 | 5.5% | |
| 18 to 44 | 959 | 10.9% | |
| 45 to 64 | 1,230 | 14% | |
| 65 to 74 | 1,180 | 13.5% | |
| 75 and over | 1,355 | 15.5% | |
| Age not given | 2,812 | 32.1% |
| Reporter | Reports | Share | Share as a bar |
|---|---|---|---|
| Physician | 2,918 | 33.3% | |
| Pharmacist | 870 | 9.9% | |
| Other health professional | 2,808 | 32% | |
| Lawyer | 4 | under 0.1% | |
| Consumer or non-health professional | 1,775 | 20.3% | |
| Not given | 389 | 4.4% |
Official pages
- MedWatch Online Voluntary Reporting FormThe online form of FDA for a voluntary report.
- MedWatch: The FDA Safety Information and Adverse Event Reporting ProgramThe page of the FDA program that receives reports about drugs and devices.
- FDA Adverse Event Monitoring System (AEMS) Public DashboardThe public dashboard of FDA for adverse event reports on drugs and biologics.
The site checked these addresses on . The links open in a new tab.
Cite this page
Reported Reactions. Antimetabolite: adverse event reports that FDA received. https://reportedreactions.com/class/antimetabolite/ Source: U.S. Food and Drug Administration, openFDA Drug Adverse Event (FAERS) files, release of . Reports received through .
Where the data come from
The counts come from the openFDA Drug Adverse Event (FAERS) bulk files, release of 29 Oct 2026. The files have the reports that FDA received through 30 Jun 2026. A drug name is the name on the report. The site matches it to a brand name or a generic name of the National Drug Code Directory of 2 Nov 2026. A class is the pharmacologic class (EPC) of the FDA label.
The class of a drug is the Established Pharmacologic Class that openFDA attaches to its reports most often. When the reports have none, it is the class in the NDC Directory. The site does not publish a report narrative, a lot number, a detail of a patient or the identity of a reporter. The record of FDA is the authority. See how the site counts reports, the data sources and the corrections page.
Questions
Which drugs are in the Antimetabolite class on this site?
Hydrea, Hydroxyurea and Thioguanine, in order of name. The class of a drug comes from the pharmacologic class (EPC) on its FDA label.
Can the table of drugs rank the drugs?
No. FDA says:
Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product.
Source: openFDA, Drug Adverse Event Overview. The site read the page on .
Common products may have a higher number of adverse events due to the higher total number of people using the product.
Source: openFDA, Drug Adverse Event Overview. The site read the page on .
Drugs also differ in the conditions that they treat and in their time on the market.
How does a person report an adverse event?
FDA runs MedWatch, a program that takes voluntary reports from health professionals, patients and consumers. The guide on how to report has the links.