Fomepizole: adverse event reports that FDA received
Active ingredient
The Green Book lists no brand name for exactly this active ingredient.
The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand.
Read this first. FDA says this about the data:
An API dataset query result cannot be used to estimate the risk associated with the product or compare one drug or device product with another. When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event. This dataset should not be the sole source of information for clinical decision-making or other assumptions about the safety or effectiveness of a product. The adverse event may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources.
FDA Center for Veterinary Medicine publishes these words. Source: Adverse Event Reports for Animal Drugs and Devices, read on . The data have the reports that FDA received through .
This page is not veterinary advice. For an animal that is ill, speak to a veterinarian.
Contacting a veterinarianHow to report to FDAFrom March 1997 to March 2014, FDA received 37 adverse event reports that name a drug with fomepizole as its active ingredient. Of the 37 reports, 29 (78.4%) are about dogs. 6 reports are about cats (16.2%).
In January to March 2026, FDA received no reports that name this drug. The signs that appear in the largest number of the 37 reports are "Depression", "Ataxia" and "Vomiting". A report is not proof that a drug caused a sign.
This page has fewer than 50 reports. The site keeps the page for its links and keeps it out of search engines.
Since the last update of the FDA data
No update is on record. The record starts when FDA adds the reports of April to June 2026.
January to March 2026 is the latest closed quarter in the data. In that quarter FDA received 0 reports that name fomepizole: 0 dog, 0 cat, 0 horse, 0 other or not given.
Signs that the reports list
A sign is a coded term from the report. The words in brackets are a plain gloss of the term. The percentage is the share of the 37 reports that list the sign. One report can list more than one sign.
The sign that is in the largest number of the reports comes first.
- Depression[dull, quiet or withdrawn]32.4%12 reports
- Ataxia[unsteady, uncoordinated movement]29.7%11 reports
- Vomiting16.2%6 reports
- Anorexia[not eating]13.5%5 reports
- Death13.5%5 reports
- Convulsion[seizure]10.8%4 reports
- Halitosis10.8%4 reports
- Hypersalivation[drooling]10.8%4 reports
- Trembling10.8%4 reports
- Cardiac arrest8.1%3 reports
- Hypotension[low blood pressure]8.1%3 reports
- Hypothermia[low body temperature]8.1%3 reports
- Lameness8.1%3 reports
- No sign[no clinical sign was reported]8.1%3 reports
Show the next 16 signs
- Tachypnoea[fast breathing]8.1%3 reports
- Vocalisation[crying out or unusual noise]8.1%3 reports
- Anaphylaxis[sudden severe allergic-type reaction]5.4%2 reports
- Diarrhoea[diarrhea]5.4%2 reports
- Dyspnoea[difficulty breathing]5.4%2 reports
- Elevated alanine aminotransferase (ALT)[a liver enzyme above the normal range]5.4%2 reports
- Elevated serum alkaline phosphatase (SAP)[a liver and bone enzyme above the normal range]5.4%2 reports
- Injection site necrosis[necrosis where the injection was given]5.4%2 reports
- Oedema of the extremities[swollen legs or paws]5.4%2 reports
- Pale mucous membrane[pale gums]5.4%2 reports
- Sedation5.4%2 reports
- Stupor[barely responsive]5.4%2 reports
- Tachycardia[fast heart rate]5.4%2 reports
- Weakness5.4%2 reports
- Accidental exposure[exposure that was not intended]2.7%1 reports
- Alopecia NOS[hair loss, type not specified]2.7%1 reports
The list shows 30 of 81 coded signs. A report is not proof that a drug caused a sign. Download all signs (CSV)
Reports by species
The share is of all 37 reports that name fomepizole. The other reports give a different species or no species.
Reports for each month, Apr 2021 to Mar 2026
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
No chart: no month has 5 or more reports.
The month is the month in which FDA received the report. Each chart has its own scale. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.
Reports by year
- Dog
- Cat
- Horse
- Other or not given
| Year | Dog | Cat | Horse | Other or not given | All species |
|---|---|---|---|---|---|
| 2014 | 1 | 0 | 0 | 0 | 1 |
| 2011 | 2 | 1 | 0 | 0 | 3 |
| 2010 | 5 | 3 | 0 | 0 | 8 |
| 2009 | 6 | 1 | 0 | 1 | 8 |
| 2007 | 0 | 0 | 0 | 1 | 1 |
| 2006 | 6 | 1 | 0 | 0 | 7 |
| 2005 | 3 | 0 | 0 | 0 | 3 |
| 2004 | 2 | 0 | 0 | 0 | 2 |
| 2003 | 2 | 0 | 0 | 0 | 2 |
| 2002 | 1 | 0 | 0 | 0 | 1 |
| 1997 | 1 | 0 | 0 | 0 | 1 |
2014 has the reports that FDA received through Mar 2014. Download the years (CSV)
What the reports record
Outcome at the time of the report
- Recovered/Normal0%0
- Recovered with Sequela[recovered, with a lasting effect]0%0
- Ongoing0%0
- Died16.2%6
- Euthanized0%0
- Outcome Unknown0%0
An outcome in a report is not proof that the drug caused it. The person who sends the report gives the outcome. Each share is of the 37 reports that name fomepizole.
A report about more than one animal can have more than one outcome.
Kind of report
- Safety issue100%37
- Lack of expected effectiveness0%0
- Both safety and lack of expected effectiveness0%0
- Manufacturing or product defect0%0
- Other0%0
Show age, weight, breed and route
Age of the animal
- Under 1 year5.4%2
- 1 to 3 years35.1%13
- 4 to 7 years27%10
- 8 to 11 years5.4%2
- 12 years and over8.1%3
- Age not given18.9%7
Weight of the animal
- Under 5 kg (11 lb)18.9%7
- 5 to 9.9 kg (11 to 22 lb)13.5%5
- 10 to 24.9 kg (22 to 55 lb)21.6%8
- 25 to 44.9 kg (55 to 99 lb)16.2%6
- 45 kg and over (99 lb and over)5.4%2
- Weight not given24.3%9
Breed, where the report gives one breed
- Labrador Retriever8.1%3
- Boston Terrier5.4%2
- Domestic2.7%1
- Akita2.7%1
- Beagle2.7%1
- Chihuahua2.7%1
- Dachshund2.7%1
- Brussels Griffon2.7%1
A breed with many animals has many reports.
Route in the report
- Intravenous54.1%20
- Ophthalmic5.4%2
- Intramuscular2.7%1
- Oral2.7%1
Each bar is on a scale of 0 to 100%.
Approved animal drugs with this active ingredient (FDA Green Book)
This section is reference data. It has no report count.
The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand.
| Brand name | Active ingredients | Sponsor | Approved species | Application |
|---|---|---|---|---|
| Antizol-Vetapproval withdrawn | Fomepizole | Paladin Labs (USA), Inc. | Dogs | NADA 141-075 |
| Fomepizole for Injectionapproval withdrawn | Fomepizole | Mylan Institutional, LLC | Not in the list of major species | ANADA 200-472 |
FDA pages for this drug
- How to Report Animal Drug and Device Side Effects and Product ProblemsThe FDA page that tells an owner or a veterinarian how to send a report.
- Animal Drugs @ FDAThe search page of the Green Book, the FDA list of approved animal drugs.
The site checked these addresses on . The links open in a new tab.
Cite this page
Pet Drug Reports. Fomepizole: adverse event reports that FDA received. https://petdrugreports.com/drug/fomepizole/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of . Reports received through .
Where the data come from
The counts come from the openFDA Animal and Veterinary adverse event files, export of 28 Sep 2026. The files have the reports that the FDA Center for Veterinary Medicine received through 31 Mar 2026. The files mask brand and manufacturer names. The site counts a drug by the active ingredients that each record gives, and gives no count to a brand, an application or a company. Ingredient names and the lists of approved products follow the FDA Green Book of 1 Oct 2026. The site does not use the application number that a record has.
The site does not publish report text, lot numbers or details of a reporter. FDA's record is the authority. See how the site counts reports, the data sources and the corrections page.
Questions about these reports
- Which brand are these reports about?
The openFDA records give the value "MSK" for the brand name and for the manufacturer name of each drug. FDA says that MSK means "masked". So the site cannot count a report for a brand. The Green Book lists no brand name for exactly this active ingredient.
- Do the reports show that the drug caused the signs?
No. FDA states this about the data.
When looking at the results, be aware that there is no certainty that the reported drug or device caused the adverse event.
The adverse event may have been related to an underlying disease, other drugs used at the same time or other non-drug related sources.
FDA Center for Veterinary Medicine. Source: Adverse Event Reports for Animal Drugs and Devices
- How many reports did FDA receive in the latest 12 months?
FDA received no reports in the 12 months to March 2026. It received no reports in the 12 months before. FDA says that a report can take 3 to 6 months to reach the public data. The newest months can get more reports in a later update.
- What kinds of report are in the count?
Of the 37 reports received from March 1997 to March 2014, 100% are about a safety issue only.