Blood problems after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 545 reports of blood problems in dogs after Ivermectin + Pyrantel. That is 0.4% of all reports for this medicine, compared with 1.8% across reports for all dog medicines, so it is reported less often than average with this medicine.

545Reports

62%Marked serious

9.7%Recovered

26%Died or euthanised

13 daysTypical onset

How soon it started

Same day

35 14%

1–2 days

48 19%

3–7 days

26 10%

1–4 weeks

54 21%

Over a month

91 36%

How the animals did

Recovered

45 8.3%

Recovered with lasting effects

8 1.5%

Still unwell when reported

108 20%

Died

73 13%

Euthanised

70 13%

Not known

241 44%

Problems reported at the same time

236 43%

205 38%

174 32%

153 28%

143 26%

112 21%

111 20%

86 16%

Age of the animals

Under 1 year

1–3 years

125

4–7 years

132

8–11 years

132

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 blood problems in dogs?: 545 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 13 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 problems with similar medicines

Blood problems after Milbemycin Oxime + Spinosad (Trifexis) 735 reports · 0.6% of its reports
Blood problems after Moxidectin (ProHeart 6) 1,343 reports · 2.7% of its reports
Blood problems after Milbemycin Oxime + Praziquantel (Interceptor Plus) 225 reports · 0.7% of its reports
Blood problems after Milbemycin Oxime (Interceptor) 251 reports · 0.8% of its reports
Blood problems after Selamectin (Revolution) 327 reports · 1.1% of its reports
Blood problems after Ivermectin (Heartgard) 145 reports · 1.2% of its reports
Blood problems after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 37 reports · 0.4% of its reports
Blood problems after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 30 reports · 2.6% of its reports

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