Loose stool after Ivermectin + Pyrantel (Heartgard Plus) in dogs

1,339 reports to the FDA describe loose stool in dogs given Ivermectin + Pyrantel. That is 0.9% of all reports for this medicine, compared with 0.9% across reports for all dog medicines.

1,339Reports

56%Marked serious

27%Recovered

1.3%Died or euthanised

16 daysTypical onset

How soon it started

Same day

177 26%

1–2 days

103 15%

3–7 days

32 4.7%

1–4 weeks

67 9.9%

Over a month

296 44%

How the animals did

Recovered

355 27%

Recovered with lasting effects

6 0.4%

Still unwell when reported

131 9.8%

Died

7 0.5%

Euthanised

10 0.7%

Not known

830 62%

Problems reported at the same time

Digestive tract disorder

440 33%

Didn't stop worms

404 30%

Vomiting

319 24%

Didn't work as expected

278 21%

208 16%

184 14%

88 6.6%

44 3.3%

Age of the animals

Under 1 year

254

1–3 years

405

4–7 years

308

8–11 years

222

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 loose stool in dogs?: 1,339 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 16 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).

Loose stool with similar medicines

Loose stool after Milbemycin Oxime + Spinosad (Trifexis) 885 reports · 0.7% of its reports
Loose stool after Moxidectin (ProHeart 6) 332 reports · 0.7% of its reports
Loose stool after Milbemycin Oxime + Praziquantel (Interceptor Plus) 406 reports · 1.3% of its reports
Loose stool after Milbemycin Oxime (Interceptor) 327 reports · 1.1% of its reports
Loose stool after Selamectin (Revolution) 156 reports · 0.5% of its reports
Loose stool after Ivermectin (Heartgard) 88 reports · 0.7% of its reports
Loose stool after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 120 reports · 1.4% of its reports

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