Leucopenia after Ivermectin + Pyrantel (Heartgard Plus) in dogs

100 reports to the FDA describe leucopenia in dogs given Ivermectin + Pyrantel. That is 0.1% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported less often than average with this medicine.

100Reports

70%Marked serious

20%Recovered

22%Died or euthanised

10 daysTypical onset

How soon it started

Same day

10 18%

1–2 days

15 26%

3–7 days

3 5.3%

1–4 weeks

8 14%

Over a month

21 37%

How the animals did

Recovered

16 16%

Recovered with lasting effects

4 4.0%

Still unwell when reported

23 23%

Died

9 9.0%

Euthanised

13 13%

Not known

35 35%

Problems reported at the same time

50 50%

39 39%

36 36%

35 35%

35 35%

29 29%

24 24%

22 22%

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 leucopenia in dogs?: 100 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).

Leucopenia with similar medicines

Leucopenia after Milbemycin Oxime + Spinosad (Trifexis) 109 reports · 0.1% of its reports
Leucopenia after Moxidectin (ProHeart 6) 198 reports · 0.4% of its reports
Leucopenia after Milbemycin Oxime + Praziquantel (Interceptor Plus) 25 reports · 0.1% of its reports
Leucopenia after Milbemycin Oxime (Interceptor) 40 reports · 0.1% of its reports
Leucopenia after Selamectin (Revolution) 47 reports · 0.2% of its reports
Leucopenia after Ivermectin (Heartgard) 35 reports · 0.3% of its reports

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