Increased heart rate after Afoxolaner (NexGard) in dogs

59 reports to the FDA describe increased heart rate in dogs given Afoxolaner. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

59Reports
42%Marked serious
37%Recovered
14%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
19 42%
1–2 days
12 27%
3–7 days
3 6.7%
1–4 weeks
3 6.7%
Over a month
8 18%

How the animals did

Recovered
22 37%
Still unwell when reported
4 6.8%
Died
6 10%
Euthanised
2 3.4%
Not known
25 42%

Problems reported at the same time

Age of the animals

Under 1 year
7
1–3 years
18
4–7 years
12
8–11 years
13
12+ years
7

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 increased heart rate in dogs?
59 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).

Increased heart rate with similar medicines

All reported side effects of Afoxolaner in dogs · Medicines most reported with increased heart rate