Nystagmus after Afoxolaner (NexGard) in dogs

The FDA has received 127 reports of nystagmus in dogs after Afoxolaner. That is 0.2% of all reports for this medicine, compared with 0.3% across reports for all dog medicines.

127Reports
47%Marked serious
29%Recovered
7.1%Died or euthanised
2 daysTypical onset
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How soon it started

Same day
27 28%
1–2 days
21 22%
3–7 days
16 17%
1–4 weeks
13 14%
Over a month
18 19%

How the animals did

Recovered
36 28%
Recovered with lasting effects
1 0.8%
Still unwell when reported
23 18%
Died
3 2.4%
Euthanised
6 4.7%
Not known
58 46%

Problems reported at the same time

Age of the animals

Under 1 year
25
1–3 years
12
4–7 years
25
8–11 years
28
12+ years
37

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 nystagmus in dogs?
127 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 2 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).

Nystagmus with similar medicines

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