Wobbliness (ataxia) after Ivermectin (Heartgard) in horses

The FDA has received 83 reports of wobbliness (ataxia) in horses after Ivermectin. That is 12% of all reports for this medicine, compared with 4.9% across reports for all horse medicines, so it is reported unusually often with this medicine.

83Reports

7.2%Marked serious

2.4%Recovered

25%Died or euthanised

–Typical onset

How the animals did

Recovered

2 2.4%

Died

21 25%

Not known

60 72%

Problems reported at the same time

Lethargy

22 27%

Death

19 23%

Eye or vision problems

16 19%

Recumbency

14 17%

Tremors

10 12%

Collapse

7 8.4%

Swelling

7 8.4%

Weakness

6 7.2%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Ivermectin prevents heartworm disease (monthly).

Products with this ingredient include Heartgard. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Some herding breeds (for example Collies) carry the MDR1 gene variant and can be more sensitive to this drug class at high doses.

Questions owners ask

Can Ivermectin cause wobbliness (ataxia) in horses?: 83 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Wobbliness (ataxia) with similar medicines

Wobbliness (ataxia) after Ivermectin + Praziquantel 34 reports · 1.3% of its reports
Wobbliness (ataxia) after Moxidectin (ProHeart 6) 273 reports · 20% of its reports
Wobbliness (ataxia) after Moxidectin + Praziquantel 34 reports · 9.1% of its reports

All reported side effects of Ivermectin in horses · Medicines most reported with wobbliness (ataxia)