Weakness after Ivermectin (Heartgard) in dogs

229 reports to the FDA describe weakness in dogs given Ivermectin. That is 1.9% of all reports for this medicine, compared with 1.4% across reports for all dog medicines.

229Reports

37%Marked serious

24%Recovered

17%Died or euthanised

39 daysTypical onset

How soon it started

Same day

17 15%

1–2 days

5 4.3%

3–7 days

14 12%

1–4 weeks

15 13%

Over a month

66 56%

How the animals did

Recovered

44 19%

Recovered with lasting effects

10 4.4%

Still unwell when reported

46 20%

Died

22 9.6%

Euthanised

16 7.0%

Not known

91 40%

Problems reported at the same time

88 38%

69 30%

53 23%

51 22%

48 21%

38 17%

Eye or vision problems

32 14%

Drooling

29 13%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Ivermectin prevents heartworm disease (monthly).

Products with this ingredient include Heartgard. 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 Ivermectin cause weakness in dogs?: 229 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 39 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).

Weakness with similar medicines

Weakness after Ivermectin + Pyrantel (Heartgard Plus) 453 reports · 0.3% of its reports
Weakness after Milbemycin Oxime + Spinosad (Trifexis) 847 reports · 0.7% of its reports
Weakness after Moxidectin (ProHeart 6) 913 reports · 1.8% of its reports
Weakness after Milbemycin Oxime + Praziquantel (Interceptor Plus) 256 reports · 0.8% of its reports
Weakness after Milbemycin Oxime (Interceptor) 223 reports · 0.7% of its reports
Weakness after Selamectin (Revolution) 214 reports · 0.7% of its reports
Weakness after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 76 reports · 0.9% of its reports

All reported side effects of Ivermectin in dogs · Medicines most reported with weakness