Weight loss after Moxidectin (ProHeart 6) in horses

35 reports to the FDA describe weight loss in horses given Moxidectin. That is 2.6% of all reports for this medicine, compared with 1.4% across reports for all horse medicines, so it is reported unusually often with this medicine.

35Reports
2.9%Marked serious
2.9%Recovered
11%Died or euthanised
–Typical onset
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How the animals did

Recovered with lasting effects
1 2.9%
Still unwell when reported
1 2.9%
Died
4 11%
Not known
29 83%

Problems reported at the same time

10 29%
Hypoalbuminaemia
4 11%
Leucocytosis
4 11%
Loss of condition
3 8.6%
3 8.6%

Age of the animals

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

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 weight loss in horses?
35 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).

Weight loss with similar medicines

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