Pet Drug Reports

Ondansetronadverse 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 FDA

From August 2008 to June 2026, FDA received 887 adverse event reports that name a drug with ondansetron as its active ingredient. Of the 887 reports, 664 (74.9%) are about dogs. 218 reports are about cats (24.6%).

In January to March 2026, FDA received 84 reports that name this drug. The signs that appear in the largest number of the 887 reports are "Lethargy", "Vomiting" and "Death by euthanasia". A report is not proof that a drug caused a sign.

Reports that name this drug rose by 26.7% in the 12 months to June 2026, compared with the 12 months before. Reports for all animal drugs fell by 4.6% in the same periods. The newest months can get more reports in a later update. Reports about cats are 24.6% of the reports that name this drug, and 11% of all reports.

Since the last update of the FDA data

The site recorded an update of the FDA data on . FDA changed these counts for January to March 2026:

  • All species: from 73 to 84.
  • Dog: from 45 to 50.
  • Cat: from 27 to 32.

January to March 2026 is the latest closed quarter in the data. In that quarter FDA received 84 reports that name ondansetron: 50 dog, 32 cat, 0 horse, 2 other or not given.

All updatesFeed of updates (RSS)

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 887 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.

  1. Lethargy[unusually tired or inactive]32.4%287 reports
  2. Vomiting30%266 reports
  3. Death by euthanasia[the animal was euthanized]20.9%185 reports
  4. Diarrhoea[diarrhea]20.4%181 reports
  5. Not eating18.8%167 reports
  6. Elevated alanine aminotransferase (ALT)[a liver enzyme above the normal range]15.8%140 reports
  7. Anorexia[not eating]14%124 reports
  8. Other abnormal test result NOS[abnormal laboratory result, type not specified]13.5%120 reports
  9. Elevated total bilirubin[bilirubin above the normal range]13.3%118 reports
  10. Weight loss12%106 reports
  11. Dehydration11.3%100 reports
  12. Abnormal ultrasound finding10.7%95 reports
  13. Decreased appetite10.6%94 reports
  14. Lack of efficacy - NOS[the product did not have the expected effect]10.5%93 reports
Show the next 16 signs
  1. Anaemia NOS[low red blood cell count]9.6%85 reports
  2. Death9.2%82 reports
  3. Elevated blood urea nitrogen (BUN)[a kidney value above the normal range]9.1%81 reports
  4. Abnormal radiograph finding9%80 reports
  5. Neutrophilia[high neutrophil count]8.9%79 reports
  6. Leucocytosis NOS[high white blood cell count]8.2%73 reports
  7. Elevated serum alkaline phosphatase (ALP)[a liver and bone enzyme above the normal range]8.1%72 reports
  8. Elevated creatinine[a kidney value above the normal range]8%71 reports
  9. Fever7.8%69 reports
  10. Hypokalaemia[low blood potassium]7.8%69 reports
  11. Behavioural disorder NOS[behaviour change, type not specified]7.6%67 reports
  12. Hypoalbuminaemia[low blood albumin]7.4%66 reports
  13. Monocytosis[high monocyte count]7.4%66 reports
  14. Hyperglycaemia[high blood sugar]6.7%59 reports
  15. Tachycardia[fast heart rate]6.7%59 reports
  16. Emesis (multiple)[vomiting more than once]6.3%56 reports

The list shows 30 of 1,122 coded signs. A report is not proof that a drug caused a sign. Download all signs (CSV)

Reports by species

  • Dog74.9%664
  • Cat24.6%218
  • Human exposure0.3%3
  • Lynx0.2%2

The share is of all 887 reports that name ondansetron. The other reports give a different species or no species.

Reports for each month, Jul 2021 to Jun 2026

Dog488 reports. Largest count in one month: 28 (Apr 2026)
Cat188 reports. Largest count in one month: 14 (Feb 2026)
Horse0 reports

No chart: no month has 5 or more reports.

Other or not given2 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
Reports that name ondansetron, by the year in which FDA received them and by species
YearDogCatHorseOther or not givenAll species
20261024502149
20251746000234
20241144600160
202363240087
20222190030
20212470031
20201660022
20191930022
20183190141
20172920132
20162000121
20151910020
201451006
20131550020
20121100011
200810001

2026 has the reports that FDA received through Jun 2026. Download the years (CSV)

What the reports record

Outcome at the time of the report

  • Recovered/Normal17.7%157
  • Recovered with Sequela[recovered, with a lasting effect]0.1%1
  • Ongoing36.5%324
  • Died9.6%85
  • Euthanized20.5%182
  • Outcome Unknown15.7%139

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 887 reports that name ondansetron.

A report about more than one animal can have more than one outcome.

Kind of report

  • Safety issue85.1%755
  • Lack of expected effectiveness2.7%24
  • Both safety and lack of expected effectiveness11.2%99
  • Manufacturing or product defect0.8%7
  • Other0.2%2

883 reports say if the event was serious. 72.4% of them have the serious flag. The person who sends the report sets the flag.

Show age, weight, breed and route

Age of the animal

  • Under 1 year8.5%75
  • 1 to 3 years16.9%150
  • 4 to 7 years24.1%214
  • 8 to 11 years23.9%212
  • 12 years and over25.1%223
  • Age not given1.5%13

Weight of the animal

  • Under 5 kg (11 lb)20.2%179
  • 5 to 9.9 kg (11 to 22 lb)25.6%227
  • 10 to 24.9 kg (22 to 55 lb)23.2%206
  • 25 to 44.9 kg (55 to 99 lb)24%213
  • 45 kg and over (99 lb and over)2.3%20
  • Weight not given4.7%42

Breed, where the report gives one breed

A breed with many animals has many reports.

Route in the report

  • Oral20.2%179
  • Intravenous10.8%96
  • Parenteral1.9%17
  • Subcutaneous1.6%14
  • Intramuscular0.3%3
  • Other0.3%3

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.

The Green Book lists no approved animal drug with this active ingredient. FDA also receives reports for human drugs and compounded drugs that veterinarians prescribe.

Next in the A to Z list

All drugs by active ingredient. Brand names A to Z

FDA pages for this drug

The site checked these addresses on . The links open in a new tab.

Cite this page

Pet Drug Reports. Ondansetron: adverse event reports that FDA received. https://petdrugreports.com/drug/ondansetron/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of . Reports received through .

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Where the data come from

The counts come from the openFDA Animal and Veterinary adverse event files, export of 30 Oct 2026. The files have the reports that the FDA Center for Veterinary Medicine received through 26 Jun 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 2 Nov 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 261 reports in the 12 months to June 2026. It received 206 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 887 reports received from August 2008 to June 2026, 85.1% are about a safety issue only. 13.9% are about a lack of expected effectiveness, alone or with a safety issue. 0.8% are about a defect of the product or its package.