Didn't work as expected after Spinosad (Comfortis) in cats

The FDA has received 1,060 reports of didn't work as expected in cats after Spinosad. That is 9.2% of all reports for this medicine, compared with 8.7% across reports for all cat medicines.

1,060Reports

1.6%Marked serious

23%Recovered

0.3%Died or euthanised

15 daysTypical onset

How soon it started

Same day

244 26%

1–2 days

34 3.6%

3–7 days

75 7.8%

1–4 weeks

362 38%

Over a month

241 25%

How the animals did

Recovered

195 18%

Recovered with lasting effects

49 4.6%

Still unwell when reported

2 0.2%

Died

3 0.3%

Not known

811 77%

Problems reported at the same time

1,019 96%

219 21%

89 8.4%

81 7.6%

40 3.8%

19 1.8%

Incorrect dose administered

14 1.3%

Restlessness or agitation

13 1.2%

Age of the animals

Under 1 year

130

1–3 years

231

4–7 years

190

8–11 years

139

12+ years

116

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 didn't work as expected in cats?: 1,060 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).

Didn't work as expected with similar medicines

Didn't work as expected after Nitenpyram (Capstar) 232 reports · 2.7% of its reports
Didn't work as expected after Imidacloprid + Moxidectin (Advantage Multi) 63 reports · 0.8% of its reports
Didn't work as expected after Imidacloprid + Pyriproxyfen 24 reports · 3.7% of its reports
Didn't work as expected after Fipronil 38 reports · 7.6% of its reports
Didn't work as expected after Fipronil + S-methoprene (Frontline Plus) 22 reports · 6.0% of its reports

All reported side effects of Spinosad in cats · Medicines most reported with didn't work as expected