Inappropriate defecation after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 217 reports of inappropriate defecation in dogs after Ivermectin + Pyrantel. That is 0.1% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

217Reports

64%Marked serious

40%Recovered

5.1%Died or euthanised

4 daysTypical onset

How soon it started

Same day

38 29%

1–2 days

25 19%

3–7 days

8 6.0%

1–4 weeks

27 20%

Over a month

35 26%

How the animals did

Recovered

83 38%

Recovered with lasting effects

3 1.4%

Still unwell when reported

27 12%

Died

7 3.2%

Euthanised

4 1.8%

Not known

93 43%

Problems reported at the same time

Seizures

67 31%

Inappropriate urination

63 29%

Vomiting

62 29%

Lethargy

49 23%

Diarrhea

34 16%

Digestive tract disorder

29 13%

Breathing problems

28 13%

Didn't stop worms

26 12%

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 inappropriate defecation in dogs?: 217 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 4 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).

Inappropriate defecation with similar medicines

Inappropriate defecation after Milbemycin Oxime + Spinosad (Trifexis) 198 reports · 0.2% of its reports
Inappropriate defecation after Moxidectin (ProHeart 6) 119 reports · 0.2% of its reports
Inappropriate defecation after Milbemycin Oxime + Praziquantel (Interceptor Plus) 83 reports · 0.3% of its reports
Inappropriate defecation after Ivermectin (Heartgard) 26 reports · 0.2% of its reports
Inappropriate defecation after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 46 reports · 0.5% of its reports

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