Swelling after Afoxolaner (NexGard) in dogs

The FDA has received 852 reports of swelling in dogs after Afoxolaner. That is 1.5% of all reports for this medicine, compared with 2.8% across reports for all dog medicines, so it is reported less often than average with this medicine.

852Reports
48%Marked serious
32%Recovered
7.4%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
326 45%
1–2 days
131 18%
3–7 days
44 6.1%
1–4 weeks
86 12%
Over a month
136 19%

How the animals did

Recovered
274 32%
Recovered with lasting effects
1 0.1%
Still unwell when reported
129 15%
Died
36 4.2%
Euthanised
27 3.2%
Not known
385 45%

Problems reported at the same time

Age of the animals

Under 1 year
185
1–3 years
230
4–7 years
236
8–11 years
126
12+ years
54

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 swelling in dogs?
852 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).

Swelling with similar medicines

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