Wobbliness (ataxia) after Moxidectin (ProHeart 6) in horses

The FDA has received 273 reports of wobbliness (ataxia) in horses after Moxidectin. That is 20% of all reports for this medicine, compared with 4.9% across reports for all horse medicines, so it is reported unusually often with this medicine.

273Reports

1.8%Marked serious

1.5%Recovered

7.0%Died or euthanised

1 daysTypical onset

How soon it started

Same day

2 18%

1–2 days

7 64%

3–7 days

2 18%

1–4 weeks

0 0.0%

Over a month

0 0.0%

How the animals did

Recovered

4 1.5%

Still unwell when reported

5 1.8%

Died

17 6.2%

Euthanised

2 0.7%

Not known

245 90%

Problems reported at the same time

Lethargy

113 41%

Locking mechanism abnormal

67 25%

Recumbency

45 16%

Loss of appetite

23 8.4%

Eye or vision problems

20 7.3%

Death

19 7.0%

Weakness

13 4.8%

Unresponsive

12 4.4%

Age of the animals

Under 1 year

136

1–3 years

4–7 years

8–11 years

12+ years

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 wobbliness (ataxia) in horses?: 273 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 1 day 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).

Wobbliness (ataxia) with similar medicines

Wobbliness (ataxia) after Ivermectin + Praziquantel 34 reports · 1.3% of its reports
Wobbliness (ataxia) after Ivermectin (Heartgard) 83 reports · 12% of its reports
Wobbliness (ataxia) after Moxidectin + Praziquantel 34 reports · 9.1% of its reports

All reported side effects of Moxidectin in horses · Medicines most reported with wobbliness (ataxia)