Didn't stop worms after Afoxolaner + Moxidectin + Pyrantel (NexGard PLUS) in dogs

The FDA has received 2,103 reports of didn't stop worms in dogs after Afoxolaner + Moxidectin + Pyrantel. That is 23% 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.

2,103Reports

0.4%Marked serious

5.8%Recovered

0.0%Died or euthanised

16 daysTypical onset

How soon it started

Same day

41 2.0%

1–2 days

150 7.2%

3–7 days

306 15%

1–4 weeks

1,420 68%

Over a month

165 7.9%

How the animals did

Recovered

122 5.8%

Still unwell when reported

482 23%

Euthanised

1 0.0%

Not known

1,498 71%

Problems reported at the same time

Didn't work as expected

133 6.3%

Diarrhea

23 1.1%

Vomiting

21 1.0%

Didn't prevent heartworm

9 0.4%

7 0.3%

6 0.3%

5 0.2%

5 0.2%

Age of the animals

Under 1 year

565

1–3 years

791

4–7 years

418

8–11 years

219

12+ years

About this medicine

Afoxolaner kills fleas and ticks; given as a monthly chewable. Moxidectin prevents heartworm disease (monthly topical, or a 6- or 12-month injection for dogs). Pyrantel treats roundworms and hookworms.

Products with this combination include NexGard PLUS. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

In 2018 the FDA alerted owners and vets that isoxazoline products have been associated with neurologic reactions such as muscle tremors, wobbliness (ataxia) and seizures, including in animals with no history of them.

Questions owners ask

Can Afoxolaner + Moxidectin + Pyrantel cause didn't stop worms in dogs?: 2,103 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 16 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 Fluralaner (Bravecto) 629 reports · 0.9% of its reports
Didn't stop worms after Afoxolaner (NexGard) 1,124 reports · 2.0% of its reports
Didn't stop worms after Sarolaner (Simparica) 388 reports · 2.3% of its reports
Didn't stop worms after Lotilaner (Credelio) 552 reports · 5.5% of its reports
Didn't stop worms after Lotilaner + Moxidectin + Praziquantel + Pyrantel (Credelio Quattro) 335 reports · 11% of its reports

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