Didn't stop fleas after Levothyroxine in dogs

The FDA has received 32 reports of didn't stop fleas in dogs after Levothyroxine. That is 1.1% of all reports for this medicine, compared with 6.2% across reports for all dog medicines, so it is reported less often than average with this medicine.

32Reports

9.4%Marked serious

16%Recovered

0.0%Died or euthanised

166 daysTypical onset

How soon it started

Same day

1 5.9%

1–2 days

0 0.0%

3–7 days

0 0.0%

1–4 weeks

2 12%

Over a month

14 82%

How the animals did

Recovered

2 6.3%

Recovered with lasting effects

3 9.4%

Still unwell when reported

4 13%

Not known

23 72%

Problems reported at the same time

Didn't work as expected

7 22%

3 9.4%

2 6.3%

2 6.3%

1 3.1%

1 3.1%

Drug dose administration interval too short

1 3.1%

Reddening of the skin

1 3.1%

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 didn't stop fleas in dogs?: 32 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 166 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).

Didn't stop fleas with similar medicines

Didn't stop fleas after Insulin 31 reports · 0.4% of its reports
Didn't stop fleas after Phenylpropanolamine (Proin) 20 reports · 0.5% of its reports

All reported side effects of Levothyroxine in dogs · Medicines most reported with didn't stop fleas