Lethargy after Ivermectin + Pyrantel (Heartgard Plus) in dogs

7,391 reports to the FDA describe lethargy in dogs given Ivermectin + Pyrantel. That is 5.0% of all reports for this medicine, compared with 11% across reports for all dog medicines, so it is reported less often than average with this medicine.

7,391Reports

43%Marked serious

33%Recovered

5.9%Died or euthanised

2 daysTypical onset

How soon it started

Same day

1,355 34%

1–2 days

759 19%

3–7 days

257 6.5%

1–4 weeks

438 11%

Over a month

1,162 29%

How the animals did

Recovered

2,394 32%

Recovered with lasting effects

74 1.0%

Still unwell when reported

639 8.6%

Died

265 3.6%

Euthanised

173 2.3%

Not known

3,846 52%

Problems reported at the same time

2,820 38%

2,400 32%

1,578 21%

582 7.9%

482 6.5%

459 6.2%

458 6.2%

421 5.7%

Age of the animals

Under 1 year

1,305

1–3 years

2,134

4–7 years

1,903

8–11 years

1,240

12+ years

546

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 lethargy in dogs?: 7,391 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 2 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).

Lethargy with similar medicines

Lethargy after Milbemycin Oxime + Spinosad (Trifexis) 19,835 reports · 15% of its reports
Lethargy after Moxidectin (ProHeart 6) 6,640 reports · 13% of its reports
Lethargy after Milbemycin Oxime + Praziquantel (Interceptor Plus) 2,407 reports · 7.6% of its reports
Lethargy after Milbemycin Oxime (Interceptor) 2,528 reports · 8.5% of its reports
Lethargy after Selamectin (Revolution) 2,964 reports · 10% of its reports
Lethargy after Ivermectin (Heartgard) 1,488 reports · 12% of its reports
Lethargy after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 969 reports · 11% of its reports
Lethargy after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 135 reports · 12% of its reports
Lethargy after Ivermectin + Praziquantel 35 reports · 17% of its reports
Lethargy after Moxidectin + Praziquantel 21 reports · 28% of its reports

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