Weight loss after Afoxolaner (NexGard) in dogs

The FDA has received 504 reports of weight loss in dogs after Afoxolaner. That is 0.9% of all reports for this medicine, compared with 1.7% across reports for all dog medicines, so it is reported less often than average with this medicine.

504Reports
59%Marked serious
12%Recovered
20%Died or euthanised
5 daysTypical onset
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How soon it started

Same day
86 23%
1–2 days
83 22%
3–7 days
34 9.0%
1–4 weeks
58 15%
Over a month
115 31%

How the animals did

Recovered
56 11%
Recovered with lasting effects
4 0.8%
Still unwell when reported
78 15%
Died
37 7.3%
Euthanised
65 13%
Not known
264 52%

Problems reported at the same time

Age of the animals

Under 1 year
45
1–3 years
97
4–7 years
110
8–11 years
145
12+ years
82

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 weight loss in dogs?
504 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).

Weight loss with similar medicines

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