Didn't stop worms after Moxidectin (ProHeart 6) in horses

55 reports to the FDA describe didn't stop worms in horses given Moxidectin. That is 4.0% of all reports for this medicine, compared with 2.1% across reports for all horse medicines, so it is reported unusually often with this medicine.

55Reports
5.5%Marked serious
5.5%Recovered
5.5%Died or euthanised
31 daysTypical onset
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How soon it started

Same day
0 0.0%
1–2 days
2 15%
3–7 days
0 0.0%
1–4 weeks
4 31%
Over a month
7 54%

How the animals did

Recovered
3 5.5%
Still unwell when reported
3 5.5%
Died
2 3.6%
Euthanised
1 1.8%
Not known
46 84%

Problems reported at the same time

11 20%
Hair modification
3 5.5%
3 5.5%
Loss of condition
2 3.6%
Crust
1 1.8%

Age of the animals

Under 1 year
2
1–3 years
15
4–7 years
2
8–11 years
1
12+ years
9

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 didn't stop worms in horses?
55 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 31 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).

Didn't stop worms with similar medicines

All reported side effects of Moxidectin in horses · Medicines most reported with didn't stop worms