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

The FDA has received 355 reports of blood in faeces in dogs after Ivermectin + Pyrantel. That is 0.2% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

355Reports

72%Marked serious

20%Recovered

4.5%Died or euthanised

27 daysTypical onset

How soon it started

Same day

35 18%

1–2 days

27 14%

3–7 days

12 6.3%

1–4 weeks

24 13%

Over a month

93 49%

How the animals did

Recovered

69 19%

Recovered with lasting effects

2 0.6%

Still unwell when reported

37 10%

Died

9 2.5%

Euthanised

7 2.0%

Not known

231 65%

Problems reported at the same time

Digestive tract disorder

184 52%

Didn't stop worms

165 46%

Vomiting

117 33%

Diarrhea

115 32%

Didn't work as expected

95 27%

Loss of appetite

78 22%

Lethargy

71 20%

Mucous stool

45 13%

Age of the animals

Under 1 year

1–3 years

143

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 blood in faeces in dogs?: 355 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 27 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 in faeces with similar medicines

Blood in faeces after Milbemycin Oxime + Spinosad (Trifexis) 215 reports · 0.2% of its reports
Blood in faeces after Moxidectin (ProHeart 6) 133 reports · 0.3% of its reports
Blood in faeces after Milbemycin Oxime + Praziquantel (Interceptor Plus) 84 reports · 0.3% of its reports
Blood in faeces after Milbemycin Oxime (Interceptor) 26 reports · 0.1% of its reports
Blood in faeces after Selamectin (Revolution) 31 reports · 0.1% of its reports
Blood in faeces after Ivermectin (Heartgard) 32 reports · 0.3% of its reports
Blood in faeces after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 26 reports · 0.3% of its reports

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