Loose stool after Ivermectin (Heartgard) in dogs

88 reports to the FDA describe loose stool in dogs given Ivermectin. That is 0.7% of all reports for this medicine, compared with 0.9% across reports for all dog medicines.

88Reports

30%Marked serious

32%Recovered

3.4%Died or euthanised

10 daysTypical onset

How soon it started

Same day

12 22%

1–2 days

7 13%

3–7 days

8 15%

1–4 weeks

5 9.1%

Over a month

23 42%

How the animals did

Recovered

21 24%

Recovered with lasting effects

7 8.0%

Still unwell when reported

26 30%

Died

2 2.3%

Euthanised

1 1.1%

Not known

31 35%

Problems reported at the same time

37 42%

24 27%

17 19%

14 16%

11 13%

9 10%

Didn't work as expected

8 9.1%

Behaviour change

7 8.0%

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 loose stool in dogs?: 88 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 10 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).

Loose stool with similar medicines

Loose stool after Ivermectin + Pyrantel (Heartgard Plus) 1,339 reports · 0.9% of its reports
Loose stool after Milbemycin Oxime + Spinosad (Trifexis) 885 reports · 0.7% of its reports
Loose stool after Moxidectin (ProHeart 6) 332 reports · 0.7% of its reports
Loose stool after Milbemycin Oxime + Praziquantel (Interceptor Plus) 406 reports · 1.3% of its reports
Loose stool after Milbemycin Oxime (Interceptor) 327 reports · 1.1% of its reports
Loose stool after Selamectin (Revolution) 156 reports · 0.5% of its reports
Loose stool after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 120 reports · 1.4% of its reports

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