Ivermectin (Ivomec, Heartgard): adverse event reports that FDA received

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 20,136 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. Vomiting10.5%2,121 reports
2. Lack of efficacy (endoparasite) - heartworm[the product did not have the expected effect: heartworm]9.2%1,860 reports
3. Ataxia[unsteady, uncoordinated movement]9.2%1,856 reports
4. Death7.8%1,565 reports
5. Emesis[vomiting]7.3%1,474 reports
6. Ineffective, heartworm larvae[legacy FDA term: the product did not have the expected effect (heartworm larvae)]7%1,419 reports
7. Lethargy[unusually tired or inactive]5.7%1,151 reports
8. Depression[dull, quiet or withdrawn]5.5%1,105 reports
9. Diarrhoea[diarrhea]4.8%972 reports
10. Accidental exposure[exposure that was not intended]4.6%927 reports
11. Anorexia[not eating]4.5%897 reports
12. Mydriasis[dilated pupils]4%813 reports
13. Trembling3.2%651 reports
14. Lack of efficacy - NOS[the product did not have the expected effect]3.1%629 reports

The list shows 30 of 1,791 coded signs. A report is not proof that a drug caused a sign. Download all signs (CSV)

Reports by species

• Dog64.5%12,989
• Cattle10.8%2,168
• Cat5%998
• Horse4.3%856
• Human exposure2.7%549
• Sheep1.2%241

The share is of all 20,136 reports that name ivermectin. The other reports give a different species or no species.

Reports for each month, Jul 2021 to Jun 2026

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

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

What the reports record

Each bar is on a scale of 0 to 100%.

Other pages with this ingredient

A report names a drug by its set of active ingredients. Each set has its own page. The list is in order of name.

• Ivermectin, all combinations
• Clorsulon + Ivermectin
• Ivermectin + Praziquantel
• Ivermectin + Praziquantel + Pyrantel Pamoate
• Ivermectin + Pyrantel Pamoate

Next in the A to Z list

• Insulin Glargine
• Isoflupredone Acetate + Neomycin Sulfate + Tetracaine Hydrochloride
• Isoflurane
• Itraconazole
• Ketamine Hydrochloride

All drugs by active ingredient. Brand names A to Z

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.
• Green Book record of NADA 128-409The FDA record of the application for Ivomec .27% Injection Grower And Feeder Pigs, Ivomec 1% Injection, Ivomec 1% Injection for Cattle And Swine, Ivomec Injection for Cattle.
• Green Book record of NADA 138-412The FDA record of the application for Heartgard 30, Heartgard Tablets.
• Green Book record of NADA 140-886The FDA record of the application for Heartgard Chewables For Dogs.
• Green Book record of ANADA 200-270The FDA record of the application for Iverhart Tablets.
• Green Book record of ANADA 200-297The FDA record of the application for Ivermectin Chewable Tablets.
• Green Book record of NADA 131-392The FDA record of the application for Ivomec Liquid.
• Animal Drugs @ FDAThe search page of the Green Book, the FDA list of approved animal drugs.

The site checked these addresses on 2 Oct 2026. The links open in a new tab.

Cite this page

Pet Drug Reports. Ivermectin: adverse event reports that FDA received. https://petdrugreports.com/drug/ivermectin/ Source: FDA Center for Veterinary Medicine, openFDA Animal and Veterinary adverse event reports, export of 30 Oct 2026. Reports received through 26 Jun 2026.

Where the data come from

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 section of this page lists the brand names with 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 263 reports in the 12 months to June 2026. It received 343 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 20,136 reports received from January 1987 to June 2026, 67.5% are about a safety issue only. 21.5% are about a lack of expected effectiveness, alone or with a safety issue. 10.9% are about a defect of the product or its package.