Lethargy after Spinosad (Comfortis) in cats

The FDA has received 1,080 reports of lethargy in cats after Spinosad. That is 9.3% of all reports for this medicine, compared with 14% across reports for all cat medicines.

1,080Reports

17%Marked serious

57%Recovered

6.8%Died or euthanised

Same dayTypical onset

How soon it started

Same day

585 63%

1–2 days

143 15%

3–7 days

41 4.4%

1–4 weeks

49 5.3%

Over a month

107 12%

How the animals did

Recovered

492 46%

Recovered with lasting effects

125 12%

Still unwell when reported

118 11%

Died

46 4.3%

Euthanised

27 2.5%

Not known

272 25%

Problems reported at the same time

523 48%

354 33%

105 9.7%

79 7.3%

78 7.2%

72 6.7%

67 6.2%

60 5.6%

Age of the animals

Under 1 year

120

1–3 years

283

4–7 years

226

8–11 years

180

12+ years

179

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 lethargy in cats?: 1,080 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 the same 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).

Lethargy with similar medicines

Lethargy after Nitenpyram (Capstar) 926 reports · 11% of its reports
Lethargy after Imidacloprid + Moxidectin (Advantage Multi) 1,394 reports · 17% of its reports
Lethargy after Lufenuron 236 reports · 21% of its reports
Lethargy after Flumethrin + Imidacloprid (Seresto) 72 reports · 11% of its reports
Lethargy after Imidacloprid + Pyriproxyfen 73 reports · 11% of its reports
Lethargy after Fipronil 62 reports · 12% of its reports
Lethargy after Fipronil + S-methoprene (Frontline Plus) 51 reports · 14% of its reports
Lethargy after Imidacloprid 33 reports · 13% of its reports

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