Abnormal ultrasound finding after Levothyroxine in dogs

The FDA has received 74 reports of abnormal ultrasound finding in dogs after Levothyroxine. That is 2.5% of all reports for this medicine, compared with 0.5% across reports for all dog medicines, so it is reported unusually often with this medicine.

74Reports

84%Marked serious

12%Recovered

32%Died or euthanised

57 daysTypical onset

How soon it started

Same day

2 4.4%

1–2 days

2 4.4%

3–7 days

2 4.4%

1–4 weeks

10 22%

Over a month

29 64%

How the animals did

Recovered

7 9.5%

Recovered with lasting effects

2 2.7%

Still unwell when reported

30 41%

Died

8 11%

Euthanised

16 22%

Not known

11 15%

Problems reported at the same time

51 69%

33 45%

24 32%

23 31%

21 28%

20 27%

20 27%

Abnormal radiograph finding

18 24%

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 abnormal ultrasound finding in dogs?: 74 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 57 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).

Abnormal ultrasound finding with similar medicines

Abnormal ultrasound finding after Trilostane (Vetoryl) 457 reports · 3.8% of its reports
Abnormal ultrasound finding after Insulin 81 reports · 1.1% of its reports
Abnormal ultrasound finding after Phenylpropanolamine (Proin) 34 reports · 0.8% of its reports

All reported side effects of Levothyroxine in dogs · Medicines most reported with abnormal ultrasound finding