Eye or vision problems after Ivermectin (Heartgard) in horses

28 reports to the FDA describe eye or vision problems in horses given Ivermectin. That is 4.1% of all reports for this medicine, compared with 0.7% across reports for all horse medicines, so it is reported unusually often with this medicine.

28Reports
11%Marked serious
3.6%Recovered
18%Died or euthanised
–Typical onset
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How the animals did

Recovered with lasting effects
1 3.6%
Died
5 18%
Not known
22 79%

Problems reported at the same time

5 18%
Breathing problems
4 14%
Tremors
4 14%

Age of the animals

Under 1 year
10
1–3 years
4
4–7 years
3
8–11 years
0
12+ years
6

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 eye or vision problems in horses?
28 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).

Eye or vision problems with similar medicines

All reported side effects of Ivermectin in horses · Medicines most reported with eye or vision problems