Leucocytosis after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 401 reports of leucocytosis in dogs after Ivermectin + Pyrantel. That is 0.3% of all reports for this medicine, compared with 1.0% across reports for all dog medicines, so it is reported less often than average with this medicine.

401Reports

66%Marked serious

15%Recovered

21%Died or euthanised

14 daysTypical onset

How soon it started

Same day

40 17%

1–2 days

38 16%

3–7 days

27 12%

1–4 weeks

45 19%

Over a month

82 35%

How the animals did

Recovered

47 12%

Recovered with lasting effects

14 3.5%

Still unwell when reported

96 24%

Died

46 11%

Euthanised

38 9.5%

Not known

160 40%

Problems reported at the same time

198 49%

183 46%

181 45%

178 44%

162 40%

112 28%

100 25%

100 25%

Age of the animals

Under 1 year

1–3 years

118

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 leucocytosis in dogs?: 401 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 14 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).

Leucocytosis with similar medicines

Leucocytosis after Milbemycin Oxime + Spinosad (Trifexis) 474 reports · 0.4% of its reports
Leucocytosis after Moxidectin (ProHeart 6) 773 reports · 1.5% of its reports
Leucocytosis after Milbemycin Oxime + Praziquantel (Interceptor Plus) 136 reports · 0.4% of its reports
Leucocytosis after Milbemycin Oxime (Interceptor) 134 reports · 0.5% of its reports
Leucocytosis after Selamectin (Revolution) 172 reports · 0.6% of its reports
Leucocytosis after Ivermectin (Heartgard) 109 reports · 0.9% of its reports
Leucocytosis after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 22 reports · 0.3% of its reports

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