Fever after Ivermectin (Heartgard) in dogs

154 reports to the FDA describe fever in dogs given Ivermectin. That is 1.3% of all reports for this medicine, compared with 1.4% across reports for all dog medicines.

154Reports

42%Marked serious

18%Recovered

22%Died or euthanised

25 daysTypical onset

How soon it started

Same day

15 20%

1–2 days

9 12%

3–7 days

4 5.4%

1–4 weeks

11 15%

Over a month

35 47%

How the animals did

Recovered

25 16%

Recovered with lasting effects

2 1.3%

Still unwell when reported

34 22%

Died

22 14%

Euthanised

12 7.8%

Not known

59 38%

Problems reported at the same time

61 40%

46 30%

45 29%

42 27%

36 23%

35 23%

Eye or vision problems

28 18%

Breathing problems

26 17%

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 fever in dogs?: 154 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 25 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).

Fever with similar medicines

Fever after Ivermectin + Pyrantel (Heartgard Plus) 597 reports · 0.4% of its reports
Fever after Milbemycin Oxime + Spinosad (Trifexis) 881 reports · 0.7% of its reports
Fever after Moxidectin (ProHeart 6) 1,914 reports · 3.8% of its reports
Fever after Milbemycin Oxime + Praziquantel (Interceptor Plus) 194 reports · 0.6% of its reports
Fever after Milbemycin Oxime (Interceptor) 255 reports · 0.9% of its reports
Fever after Selamectin (Revolution) 322 reports · 1.1% of its reports
Fever after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 33 reports · 0.4% of its reports
Fever after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 20 reports · 1.7% of its reports

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