Abnormal ultrasound finding after Afoxolaner (NexGard) in dogs

162 reports to the FDA describe abnormal ultrasound finding in dogs given Afoxolaner. That is 0.3% of all reports for this medicine, compared with 0.5% across reports for all dog medicines, so it is reported less often than average with this medicine.

162Reports
77%Marked serious
17%Recovered
33%Died or euthanised
5 daysTypical onset
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How soon it started

Same day
20 17%
1–2 days
30 26%
3–7 days
12 10%
1–4 weeks
19 16%
Over a month
35 30%

How the animals did

Recovered
24 15%
Recovered with lasting effects
3 1.9%
Still unwell when reported
32 20%
Died
23 14%
Euthanised
30 19%
Not known
50 31%

Problems reported at the same time

Age of the animals

Under 1 year
11
1–3 years
22
4–7 years
53
8–11 years
55
12+ years
20

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 abnormal ultrasound finding in dogs?
162 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 5 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).

Abnormal ultrasound finding with similar medicines

All reported side effects of Afoxolaner in dogs · Medicines most reported with abnormal ultrasound finding