Didn't prevent heartworm after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) in dogs

The FDA has received 1,879 reports of didn't prevent heartworm in dogs after Ivermectin + Praziquantel + Pyrantel. That is 22% of all reports for this medicine, compared with 13% across reports for all dog medicines, so it is reported unusually often with this medicine.

1,879Reports

19%Marked serious

7.3%Recovered

1.3%Died or euthanised

276 daysTypical onset

How soon it started

Same day

42 11%

1–2 days

0 0.0%

3–7 days

2 0.5%

1–4 weeks

12 3.1%

Over a month

333 86%

How the animals did

Recovered

84 4.5%

Recovered with lasting effects

54 2.9%

Still unwell when reported

84 4.5%

Died

18 1.0%

Euthanised

6 0.3%

Not known

1,633 87%

Problems reported at the same time

Didn't work as expected

262 14%

Drug dose administration interval too long

100 5.3%

Drug dose omission

82 4.4%

Underdose

51 2.7%

Abnormal radiograph finding

36 1.9%

Cough

29 1.5%

Overdose

26 1.4%

Death

23 1.2%

Age of the animals

Under 1 year

1–3 years

900

4–7 years

601

8–11 years

265

12+ years

About this medicine

Ivermectin prevents heartworm disease (monthly). Praziquantel treats tapeworms. Pyrantel treats roundworms and hookworms.

Products with this combination include Iverhart Max. 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 + Praziquantel + Pyrantel cause didn't prevent heartworm in dogs?: 1,879 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 276 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 prevent heartworm with similar medicines

Didn't prevent heartworm after Ivermectin + Pyrantel (Heartgard Plus) 57,581 reports · 39% of its reports
Didn't prevent heartworm after Milbemycin Oxime + Spinosad (Trifexis) 10,801 reports · 8.3% of its reports
Didn't prevent heartworm after Moxidectin (ProHeart 6) 11,529 reports · 23% of its reports
Didn't prevent heartworm after Milbemycin Oxime + Praziquantel (Interceptor Plus) 8,433 reports · 27% of its reports
Didn't prevent heartworm after Milbemycin Oxime (Interceptor) 13,118 reports · 44% of its reports
Didn't prevent heartworm after Selamectin (Revolution) 8,789 reports · 30% of its reports
Didn't prevent heartworm after Ivermectin (Heartgard) 3,385 reports · 28% of its reports
Didn't prevent heartworm after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 319 reports · 28% of its reports

All reported side effects of Ivermectin + Praziquantel + Pyrantel in dogs · Medicines most reported with didn't prevent heartworm