Muscle stiffness after Spinosad (Comfortis) in dogs

54 reports to the FDA describe muscle stiffness in dogs given Spinosad. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

54Reports

22%Marked serious

33%Recovered

11%Died or euthanised

1 daysTypical onset

How soon it started

Same day

10 45%

1–2 days

4 18%

3–7 days

2 9.1%

1–4 weeks

1 4.5%

Over a month

5 23%

How the animals did

Recovered

13 24%

Recovered with lasting effects

5 9.3%

Still unwell when reported

1 1.9%

Died

5 9.3%

Euthanised

1 1.9%

Not known

29 54%

Problems reported at the same time

18 33%

13 24%

11 20%

8 15%

8 15%

7 13%

6 11%

5 9.3%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Spinosad kills fleas; monthly chewable.

Products with this ingredient include Comfortis. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Questions owners ask

Can Spinosad cause muscle stiffness in dogs?: 54 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 1 day 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).

All reported side effects of Spinosad in dogs · Medicines most reported with muscle stiffness