Blood in faeces after Ivermectin (Heartgard) in dogs

The FDA has received 32 reports of blood in faeces in dogs after Ivermectin. That is 0.3% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

32Reports

56%Marked serious

31%Recovered

16%Died or euthanised

104 daysTypical onset

How soon it started

Same day

4 18%

1–2 days

3 14%

3–7 days

3 14%

1–4 weeks

0 0.0%

Over a month

12 55%

How the animals did

Recovered

8 25%

Recovered with lasting effects

2 6.3%

Still unwell when reported

6 19%

Died

3 9.4%

Euthanised

2 6.3%

Not known

11 34%

Problems reported at the same time

18 56%

15 47%

11 34%

9 28%

7 22%

6 19%

Didn't work as expected

6 19%

Liver problems

6 19%

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 blood in faeces in dogs?: 32 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 104 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).

Blood in faeces with similar medicines

Blood in faeces after Ivermectin + Pyrantel (Heartgard Plus) 355 reports · 0.2% of its reports
Blood in faeces after Milbemycin Oxime + Spinosad (Trifexis) 215 reports · 0.2% of its reports
Blood in faeces after Moxidectin (ProHeart 6) 133 reports · 0.3% of its reports
Blood in faeces after Milbemycin Oxime + Praziquantel (Interceptor Plus) 84 reports · 0.3% of its reports
Blood in faeces after Milbemycin Oxime (Interceptor) 26 reports · 0.1% of its reports
Blood in faeces after Selamectin (Revolution) 31 reports · 0.1% of its reports
Blood in faeces after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 26 reports · 0.3% of its reports

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