Lethargy after Ondansetron in dogs

The FDA has received 231 reports of lethargy in dogs after Ondansetron. That is 35% of all reports for this medicine, compared with 11% across reports for all dog medicines, so it is reported unusually often with this medicine.

231Reports
84%Marked serious
10.0%Recovered
44%Died or euthanised
3 daysTypical onset
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How soon it started

Same day
53 26%
1–2 days
37 18%
3–7 days
22 11%
1–4 weeks
45 22%
Over a month
46 23%

How the animals did

Recovered
23 10.0%
Still unwell when reported
83 36%
Died
33 14%
Euthanised
68 29%
Not known
24 10%

Problems reported at the same time

Age of the animals

Under 1 year
17
1–3 years
51
4–7 years
71
8–11 years
64
12+ years
24

About this medicine

Type: medicine.

Questions owners ask

Can Ondansetron cause lethargy in dogs?
231 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 3 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).

Lethargy with similar medicines

All reported side effects of Ondansetron in dogs · Medicines most reported with lethargy