Itching after Ivermectin (Heartgard) in horses

26 reports to the FDA describe itching in horses given Ivermectin. That is 3.8% of all reports for this medicine, compared with 2.2% across reports for all horse medicines, so it is reported unusually often with this medicine.

26Reports
3.8%Marked serious
0.0%Recovered
7.7%Died or euthanised
–Typical onset
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How the animals did

Died
2 7.7%
Not known
24 92%

Problems reported at the same time

Hyperaesthesia
4 15%
Hair loss
4 15%
Drooling
4 15%

Age of the animals

Under 1 year
2
1–3 years
1
4–7 years
4
8–11 years
5
12+ years
7

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 itching in horses?
26 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).

Itching with similar medicines

All reported side effects of Ivermectin in horses · Medicines most reported with itching