Eosinophilia after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 132 reports of eosinophilia in dogs after Ivermectin + Pyrantel. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

132Reports

63%Marked serious

19%Recovered

1.5%Died or euthanised

39 daysTypical onset

How soon it started

Same day

8 12%

1–2 days

6 8.7%

3–7 days

4 5.8%

1–4 weeks

15 22%

Over a month

36 52%

How the animals did

Recovered

13 9.8%

Recovered with lasting effects

12 9.1%

Still unwell when reported

28 21%

Died

2 1.5%

Not known

77 58%

Problems reported at the same time

Didn't prevent heartworm

37 28%

36 27%

29 22%

28 21%

27 20%

Digestive tract disorder

27 20%

Leucocytosis

26 20%

Diarrhea

26 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). Pyrantel treats roundworms and hookworms.

Products with this combination include Heartgard Plus, Tri-Heart Plus, Iverhart Plus. 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 + Pyrantel cause eosinophilia in dogs?: 132 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 39 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).

Eosinophilia with similar medicines

Eosinophilia after Milbemycin Oxime + Spinosad (Trifexis) 122 reports · 0.1% of its reports
Eosinophilia after Moxidectin (ProHeart 6) 79 reports · 0.2% of its reports
Eosinophilia after Milbemycin Oxime + Praziquantel (Interceptor Plus) 62 reports · 0.2% of its reports
Eosinophilia after Milbemycin Oxime (Interceptor) 39 reports · 0.1% of its reports
Eosinophilia after Selamectin (Revolution) 39 reports · 0.1% of its reports

All reported side effects of Ivermectin + Pyrantel in dogs · Medicines most reported with eosinophilia