Tremors after Spinosad (Comfortis) in cats

The FDA has received 76 reports of tremors in cats after Spinosad. That is 0.7% of all reports for this medicine, compared with 2.6% across reports for all cat medicines, so it is reported less often than average with this medicine.

76Reports

38%Marked serious

55%Recovered

9.2%Died or euthanised

1 daysTypical onset

How soon it started

Same day

29 45%

1–2 days

7 11%

3–7 days

5 7.8%

1–4 weeks

8 13%

Over a month

15 23%

How the animals did

Recovered

36 47%

Recovered with lasting effects

6 7.9%

Still unwell when reported

12 16%

Died

6 7.9%

Euthanised

1 1.3%

Not known

15 20%

Problems reported at the same time

24 32%

20 26%

17 22%

15 20%

14 18%

12 16%

9 12%

8 11%

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 tremors in cats?: 76 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).

Tremors with similar medicines

Tremors after Nitenpyram (Capstar) 205 reports · 2.3% of its reports
Tremors after Imidacloprid + Moxidectin (Advantage Multi) 413 reports · 5.1% of its reports

All reported side effects of Spinosad in cats · Medicines most reported with tremors