Didn't work as expected after Ivermectin + Pyrantel (Heartgard Plus) in dogs

27,781 reports to the FDA describe didn't work as expected in dogs given Ivermectin + Pyrantel. That is 19% of all reports for this medicine, compared with 13% across reports for all dog medicines.

27,781Reports

53%Marked serious

9.6%Recovered

0.3%Died or euthanised

59 daysTypical onset

How soon it started

Same day

135 1.3%

1–2 days

320 3.2%

3–7 days

672 6.7%

1–4 weeks

3,162 31%

Over a month

5,793 57%

How the animals did

Recovered

797 2.9%

Recovered with lasting effects

1,872 6.7%

Still unwell when reported

2,615 9.4%

Died

47 0.2%

Euthanised

28 0.1%

Not known

22,422 81%

Problems reported at the same time

Digestive tract disorder

9,778 35%

Didn't stop worms

6,947 25%

Didn't prevent heartworm

3,353 12%

Cardiac disorder

2,947 11%

Diarrhea

1,187 4.3%

Vomiting

682 2.5%

Drug dose administration interval too long

356 1.3%

Underdose

330 1.2%

Age of the animals

Under 1 year

2,654

1–3 years

9,893

4–7 years

7,951

8–11 years

4,991

12+ years

1,370

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 didn't work as expected in dogs?: 27,781 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 59 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).

Didn't work as expected with similar medicines

Didn't work as expected after Milbemycin Oxime + Spinosad (Trifexis) 13,050 reports · 10% of its reports
Didn't work as expected after Moxidectin (ProHeart 6) 2,005 reports · 4.0% of its reports
Didn't work as expected after Milbemycin Oxime + Praziquantel (Interceptor Plus) 3,979 reports · 13% of its reports
Didn't work as expected after Milbemycin Oxime (Interceptor) 3,131 reports · 11% of its reports
Didn't work as expected after Selamectin (Revolution) 2,253 reports · 7.7% of its reports
Didn't work as expected after Ivermectin (Heartgard) 741 reports · 6.2% of its reports
Didn't work as expected after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 1,337 reports · 16% of its reports
Didn't work as expected after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 123 reports · 11% of its reports

All reported side effects of Ivermectin + Pyrantel in dogs · Medicines most reported with didn't work as expected