Weakness after Ivermectin + Pyrantel (Heartgard Plus) in dogs

453 reports to the FDA describe weakness in dogs given Ivermectin + Pyrantel. That is 0.3% of all reports for this medicine, compared with 1.4% across reports for all dog medicines, so it is reported less often than average with this medicine.

453Reports

57%Marked serious

24%Recovered

17%Died or euthanised

2 daysTypical onset

How soon it started

Same day

77 32%

1–2 days

50 21%

3–7 days

20 8.2%

1–4 weeks

29 12%

Over a month

67 28%

How the animals did

Recovered

96 21%

Recovered with lasting effects

11 2.4%

Still unwell when reported

80 18%

Died

37 8.2%

Euthanised

38 8.4%

Not known

191 42%

Problems reported at the same time

168 37%

142 31%

136 30%

96 21%

88 19%

72 16%

70 15%

62 14%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

108

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 weakness in dogs?: 453 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).

Weakness with similar medicines

Weakness after Milbemycin Oxime + Spinosad (Trifexis) 847 reports · 0.7% of its reports
Weakness after Moxidectin (ProHeart 6) 913 reports · 1.8% of its reports
Weakness after Milbemycin Oxime + Praziquantel (Interceptor Plus) 256 reports · 0.8% of its reports
Weakness after Milbemycin Oxime (Interceptor) 223 reports · 0.7% of its reports
Weakness after Selamectin (Revolution) 214 reports · 0.7% of its reports
Weakness after Ivermectin (Heartgard) 229 reports · 1.9% of its reports
Weakness after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 76 reports · 0.9% of its reports

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