Didn't stop worms after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) in dogs

The FDA has received 1,299 reports of didn't stop worms in dogs after Ivermectin + Praziquantel + Pyrantel. That is 15% of all reports for this medicine, compared with 8.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

1,299Reports

3.5%Marked serious

9.3%Recovered

0.5%Died or euthanised

18 daysTypical onset

How soon it started

Same day

48 5.6%

1–2 days

40 4.7%

3–7 days

100 12%

1–4 weeks

538 63%

Over a month

126 15%

How the animals did

Recovered

121 9.3%

Still unwell when reported

16 1.2%

Died

6 0.5%

Euthanised

1 0.1%

Not known

1,155 89%

Problems reported at the same time

Didn't work as expected

492 38%

105 8.1%

46 3.5%

26 2.0%

25 1.9%

22 1.7%

21 1.6%

Drug dose administration interval too long

19 1.5%

Age of the animals

Under 1 year

136

1–3 years

468

4–7 years

339

8–11 years

218

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 stop worms in dogs?: 1,299 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 18 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 stop worms with similar medicines

Didn't stop worms after Ivermectin + Pyrantel (Heartgard Plus) 32,467 reports · 22% of its reports
Didn't stop worms after Milbemycin Oxime + Spinosad (Trifexis) 4,483 reports · 3.5% of its reports
Didn't stop worms after Moxidectin (ProHeart 6) 9,537 reports · 19% of its reports
Didn't stop worms after Milbemycin Oxime + Praziquantel (Interceptor Plus) 6,097 reports · 19% of its reports
Didn't stop worms after Milbemycin Oxime (Interceptor) 4,308 reports · 14% of its reports
Didn't stop worms after Selamectin (Revolution) 2,317 reports · 7.9% of its reports
Didn't stop worms after Ivermectin (Heartgard) 254 reports · 2.1% of its reports
Didn't stop worms after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 132 reports · 11% of its reports

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