Hind limb paresis after Spinosad (Comfortis) in dogs

The FDA has received 56 reports of hind limb paresis in dogs after Spinosad. That is 0.1% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported less often than average with this medicine.

56Reports

25%Marked serious

21%Recovered

14%Died or euthanised

156 daysTypical onset

How soon it started

Same day

2 20%

1–2 days

1 10%

3–7 days

0 0.0%

1–4 weeks

1 10%

Over a month

6 60%

How the animals did

Recovered

8 14%

Recovered with lasting effects

4 7.1%

Still unwell when reported

1 1.8%

Died

8 14%

Not known

35 63%

Problems reported at the same time

22 39%

22 39%

14 25%

11 20%

10 18%

9 16%

9 16%

8 14%

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 hind limb paresis in dogs?: 56 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 156 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).

Hind limb paresis with similar medicines

Hind limb paresis after Lufenuron + Milbemycin Oxime (Sentinel) 39 reports · 0.1% of its reports
Hind limb paresis after Imidacloprid + Moxidectin (Advantage Multi) 21 reports · 0.2% of its reports

All reported side effects of Spinosad in dogs · Medicines most reported with hind limb paresis