Decreased packed cell volume (pcv) after Afoxolaner (NexGard) in dogs

83 reports to the FDA describe decreased packed cell volume (pcv) in dogs given Afoxolaner. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

83Reports
77%Marked serious
8.4%Recovered
35%Died or euthanised
4 daysTypical onset
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How soon it started

Same day
8 13%
1–2 days
19 30%
3–7 days
10 16%
1–4 weeks
15 23%
Over a month
12 19%

How the animals did

Recovered
7 8.4%
Still unwell when reported
21 25%
Died
8 9.6%
Euthanised
21 25%
Not known
26 31%

Problems reported at the same time

Age of the animals

Under 1 year
25
1–3 years
12
4–7 years
23
8–11 years
14
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 decreased packed cell volume (pcv) in dogs?
83 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 4 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).

Decreased packed cell volume (pcv) with similar medicines

All reported side effects of Afoxolaner in dogs · Medicines most reported with decreased packed cell volume (pcv)