Restlessness or agitation after Levothyroxine in dogs

The FDA has received 125 reports of restlessness or agitation in dogs after Levothyroxine. That is 4.2% of all reports for this medicine, compared with 1.6% across reports for all dog medicines, so it is reported unusually often with this medicine.

125Reports

54%Marked serious

39%Recovered

8.8%Died or euthanised

15 daysTypical onset

How soon it started

Same day

16 19%

1–2 days

9 11%

3–7 days

12 14%

1–4 weeks

14 17%

Over a month

32 39%

How the animals did

Recovered

47 38%

Recovered with lasting effects

2 1.6%

Still unwell when reported

25 20%

Died

2 1.6%

Euthanised

9 7.2%

Not known

40 32%

Problems reported at the same time

50 40%

29 23%

28 22%

23 18%

21 17%

20 16%

19 15%

18 14%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Levothyroxine treats an underactive thyroid.

Questions owners ask

Can Levothyroxine cause restlessness or agitation in dogs?: 125 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 15 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).

Restlessness or agitation with similar medicines

Restlessness or agitation after Trilostane (Vetoryl) 247 reports · 2.1% of its reports
Restlessness or agitation after Insulin 84 reports · 1.1% of its reports
Restlessness or agitation after Phenylpropanolamine (Proin) 454 reports · 11% of its reports

All reported side effects of Levothyroxine in dogs · Medicines most reported with restlessness or agitation