Lethargy after Spinosad (Comfortis) in dogs

7,303 reports to the FDA describe lethargy in dogs given Spinosad. That is 13% of all reports for this medicine, compared with 11% across reports for all dog medicines.

7,303Reports

14%Marked serious

39%Recovered

5.0%Died or euthanised

Same dayTypical onset

How soon it started

Same day

1,758 52%

1–2 days

539 16%

3–7 days

111 3.3%

1–4 weeks

179 5.3%

Over a month

815 24%

How the animals did

Recovered

2,198 30%

Recovered with lasting effects

643 8.8%

Still unwell when reported

305 4.2%

Died

271 3.7%

Euthanised

93 1.3%

Not known

3,793 52%

Problems reported at the same time

3,321 45%

1,962 27%

950 13%

680 9.3%

544 7.4%

521 7.1%

429 5.9%

354 4.8%

Age of the animals

Under 1 year

1,010

1–3 years

2,656

4–7 years

1,832

8–11 years

1,031

12+ years

451

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 dogs?: 7,303 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 Lufenuron + Milbemycin Oxime (Sentinel) 2,341 reports · 9.0% of its reports
Lethargy after Imidacloprid + Moxidectin (Advantage Multi) 2,000 reports · 15% of its reports
Lethargy after Nitenpyram (Capstar) 1,204 reports · 11% of its reports
Lethargy after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 666 reports · 6.7% of its reports
Lethargy after Fipronil + S-methoprene (Frontline Plus) 447 reports · 15% of its reports
Lethargy after Flumethrin + Imidacloprid (Seresto) 250 reports · 11% of its reports
Lethargy after Imidacloprid 196 reports · 10% of its reports
Lethargy after Fipronil 185 reports · 13% of its reports
Lethargy after Lufenuron 205 reports · 20% of its reports
Lethargy after Imidacloprid + Permethrin + Pyriproxyfen 106 reports · 14% of its reports

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