Behaviour change after Ivermectin (Heartgard) in dogs

The FDA has received 368 reports of behaviour change in dogs after Ivermectin. That is 3.1% of all reports for this medicine, compared with 2.5% across reports for all dog medicines.

368Reports

41%Marked serious

43%Recovered

11%Died or euthanised

31 daysTypical onset

How soon it started

Same day

48 21%

1–2 days

22 9.4%

3–7 days

16 6.9%

1–4 weeks

27 12%

Over a month

120 52%

How the animals did

Recovered

134 36%

Recovered with lasting effects

26 7.1%

Still unwell when reported

61 17%

Died

16 4.3%

Euthanised

23 6.3%

Not known

108 29%

Problems reported at the same time

107 29%

101 27%

69 19%

66 18%

56 15%

Eye or vision problems

46 13%

Drooling

44 12%

Seizures

44 12%

Age of the animals

Under 1 year

1–3 years

110

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 behaviour change in dogs?: 368 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).

Behaviour change with similar medicines

Behaviour change after Ivermectin + Pyrantel (Heartgard Plus) 1,674 reports · 1.1% of its reports
Behaviour change after Milbemycin Oxime + Spinosad (Trifexis) 4,099 reports · 3.2% of its reports
Behaviour change after Moxidectin (ProHeart 6) 688 reports · 1.4% of its reports
Behaviour change after Milbemycin Oxime + Praziquantel (Interceptor Plus) 852 reports · 2.7% of its reports
Behaviour change after Milbemycin Oxime (Interceptor) 364 reports · 1.2% of its reports
Behaviour change after Selamectin (Revolution) 652 reports · 2.2% of its reports
Behaviour change after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 146 reports · 1.7% of its reports
Behaviour change after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 55 reports · 4.7% of its reports

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