Loss of consciousness after Moxidectin (ProHeart 6) in horses

The FDA has received 31 reports of loss of consciousness in horses after Moxidectin. That is 2.3% of all reports for this medicine, compared with 0.3% across reports for all horse medicines, so it is reported unusually often with this medicine.

31Reports
0.0%Marked serious
0.0%Recovered
42%Died or euthanised
–Typical onset
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How the animals did

Died
13 42%
Not known
18 58%

Problems reported at the same time

13 42%
Hypothermia
4 13%
2 6.5%
Pr-lung(s), lesion(s)
1 3.2%

Age of the animals

Under 1 year
26
1–3 years
1
4–7 years
0
8–11 years
0
12+ years
1

About this medicine

Moxidectin prevents heartworm disease (monthly topical, or a 6- or 12-month injection for dogs).

Products with this ingredient include ProHeart 6, ProHeart 12. 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 Moxidectin cause loss of consciousness in horses?
31 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).

All reported side effects of Moxidectin in horses · Medicines most reported with loss of consciousness