Unresponsive after Ivermectin (Heartgard) in dogs

The FDA has received 128 reports of unresponsive in dogs after Ivermectin. That is 1.1% of all reports for this medicine, compared with 0.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

128Reports

38%Marked serious

13%Recovered

29%Died or euthanised

11 daysTypical onset

How soon it started

Same day

12 29%

1–2 days

1 2.4%

3–7 days

4 9.8%

1–4 weeks

9 22%

Over a month

15 37%

How the animals did

Recovered

14 11%

Recovered with lasting effects

2 1.6%

Still unwell when reported

13 10%

Died

30 23%

Euthanised

7 5.5%

Not known

62 48%

Problems reported at the same time

Wobbliness (ataxia)

40 31%

Death

37 29%

Tremors

36 28%

Eye or vision problems

35 27%

31 24%

31 24%

28 22%

25 20%

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 unresponsive in dogs?: 128 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 11 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).

Unresponsive with similar medicines

Unresponsive after Ivermectin + Pyrantel (Heartgard Plus) 216 reports · 0.1% of its reports
Unresponsive after Milbemycin Oxime + Spinosad (Trifexis) 331 reports · 0.3% of its reports
Unresponsive after Moxidectin (ProHeart 6) 266 reports · 0.5% of its reports
Unresponsive after Milbemycin Oxime + Praziquantel (Interceptor Plus) 77 reports · 0.2% of its reports
Unresponsive after Milbemycin Oxime (Interceptor) 59 reports · 0.2% of its reports
Unresponsive after Selamectin (Revolution) 57 reports · 0.2% of its reports
Unresponsive after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 21 reports · 0.2% of its reports

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