Abnormal stool colouration after Afoxolaner (NexGard) in dogs

99 reports to the FDA describe abnormal stool colouration in dogs given Afoxolaner. That is 0.2% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported unusually often with this medicine.

99Reports
47%Marked serious
24%Recovered
12%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
18 23%
1–2 days
30 38%
3–7 days
6 7.7%
1–4 weeks
10 13%
Over a month
14 18%

How the animals did

Recovered
24 24%
Still unwell when reported
13 13%
Died
6 6.1%
Euthanised
6 6.1%
Not known
50 51%

Problems reported at the same time

Age of the animals

Under 1 year
14
1–3 years
26
4–7 years
22
8–11 years
22
12+ years
13

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 stool colouration in dogs?
99 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).

Abnormal stool colouration with similar medicines

All reported side effects of Afoxolaner in dogs · Medicines most reported with abnormal stool colouration