Diarrhea after Ivermectin (Heartgard) in dogs

The FDA has received 693 reports of diarrhea in dogs after Ivermectin. That is 5.8% of all reports for this medicine, compared with 8.4% across reports for all dog medicines.

693Reports

31%Marked serious

31%Recovered

8.5%Died or euthanised

15 daysTypical onset

How soon it started

Same day

83 21%

1–2 days

61 16%

3–7 days

27 7.0%

1–4 weeks

50 13%

Over a month

167 43%

How the animals did

Recovered

188 27%

Recovered with lasting effects

30 4.3%

Still unwell when reported

141 20%

Died

28 4.0%

Euthanised

31 4.5%

Not known

275 40%

Problems reported at the same time

362 52%

183 26%

171 25%

65 9.4%

59 8.5%

55 7.9%

53 7.6%

49 7.1%

Age of the animals

Under 1 year

110

1–3 years

186

4–7 years

167

8–11 years

128

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 diarrhea in dogs?: 693 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 15 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).

Diarrhea with similar medicines

Diarrhea after Ivermectin + Pyrantel (Heartgard Plus) 9,076 reports · 6.1% of its reports
Diarrhea after Milbemycin Oxime + Spinosad (Trifexis) 7,183 reports · 5.5% of its reports
Diarrhea after Moxidectin (ProHeart 6) 4,291 reports · 8.5% of its reports
Diarrhea after Milbemycin Oxime + Praziquantel (Interceptor Plus) 2,695 reports · 8.5% of its reports
Diarrhea after Milbemycin Oxime (Interceptor) 2,873 reports · 9.7% of its reports
Diarrhea after Selamectin (Revolution) 1,974 reports · 6.7% of its reports
Diarrhea after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 954 reports · 11% of its reports
Diarrhea after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 125 reports · 11% of its reports

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