Blood in faeces after Afoxolaner (NexGard) in dogs

180 reports to the FDA describe blood in faeces in dogs given Afoxolaner. That is 0.3% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

180Reports
46%Marked serious
32%Recovered
6.7%Died or euthanised
2 daysTypical onset
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How soon it started

Same day
35 21%
1–2 days
52 32%
3–7 days
12 7.4%
1–4 weeks
26 16%
Over a month
38 23%

How the animals did

Recovered
58 32%
Still unwell when reported
20 11%
Died
6 3.3%
Euthanised
6 3.3%
Not known
90 50%

Problems reported at the same time

Age of the animals

Under 1 year
25
1–3 years
54
4–7 years
45
8–11 years
32
12+ years
15

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 blood in faeces in dogs?
180 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).

Blood in faeces with similar medicines

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