Fever after Afoxolaner (NexGard) in dogs

The FDA has received 681 reports of fever in dogs after Afoxolaner. That is 1.2% of all reports for this medicine, compared with 1.4% across reports for all dog medicines.

681Reports

63%Marked serious

28%Recovered

12%Died or euthanised

1 daysTypical onset

How soon it started

Same day

212 38%

1–2 days

126 23%

3–7 days

56 10%

1–4 weeks

47 8.4%

Over a month

117 21%

How the animals did

Recovered

184 27%

Recovered with lasting effects

4 0.6%

Still unwell when reported

105 15%

Died

38 5.6%

Euthanised

47 6.9%

Not known

303 44%

Problems reported at the same time

323 47%

258 38%

184 27%

133 20%

128 19%

121 18%

106 16%

92 14%

Age of the animals

Under 1 year

133

1–3 years

183

4–7 years

165

8–11 years

140

12+ years

About this medicine

Afoxolaner kills fleas and ticks; given as a monthly chewable.

Products with this ingredient include NexGard. 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 cause fever in dogs?: 681 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 1 day 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).

Fever with similar medicines

Fever after Fluralaner (Bravecto) 638 reports · 0.9% of its reports
Fever after Sarolaner (Simparica) 187 reports · 1.1% of its reports
Fever after Lotilaner (Credelio) 129 reports · 1.3% of its reports
Fever after Afoxolaner + Moxidectin + Pyrantel (NexGard PLUS) 50 reports · 0.5% of its reports
Fever after Lotilaner + Moxidectin + Praziquantel + Pyrantel (Credelio Quattro) 39 reports · 1.3% of its reports

All reported side effects of Afoxolaner in dogs · Medicines most reported with fever