Locking mechanism abnormal after Moxidectin (ProHeart 6) in horses

The FDA has received 289 reports of locking mechanism abnormal in horses after Moxidectin. That is 21% of all reports for this medicine, compared with 1.9% across reports for all horse medicines, so it is reported unusually often with this medicine.

289Reports
0.0%Marked serious
0.0%Recovered
3.1%Died or euthanised
–Typical onset
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How the animals did

Died
9 3.1%
Not known
280 97%

Problems reported at the same time

Age of the animals

Under 1 year
128
1–3 years
47
4–7 years
11
8–11 years
4
12+ years
17

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 locking mechanism abnormal in horses?
289 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 locking mechanism abnormal