Death after Moxidectin (ProHeart 6) in horses

The FDA has received 177 reports of death in horses after Moxidectin. That is 13% of all reports for this medicine, compared with 11% across reports for all horse medicines.

177Reports
11%Marked serious
0.0%Recovered
98%Died or euthanised
2 daysTypical onset
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How soon it started

Same day
3 21%
1–2 days
5 36%
3–7 days
4 29%
1–4 weeks
0 0.0%
Over a month
2 14%

How the animals did

Died
167 94%
Euthanised
7 4.0%
Not known
3 1.7%

Problems reported at the same time

Age of the animals

Under 1 year
35
1–3 years
29
4–7 years
15
8–11 years
15
12+ years
57

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 death in horses?
177 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.
How soon after a dose was it reported?
In half of the reports with dates, it started within 2 days of the first dose.
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).

Death with similar medicines

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