Monocytosis after Spinosad (Comfortis) in dogs

The FDA has received 57 reports of monocytosis 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.

57Reports

49%Marked serious

11%Recovered

33%Died or euthanised

4 daysTypical onset

How soon it started

Same day

3 14%

1–2 days

5 24%

3–7 days

3 14%

1–4 weeks

3 14%

Over a month

7 33%

How the animals did

Recovered

2 3.5%

Recovered with lasting effects

4 7.0%

Still unwell when reported

5 8.8%

Died

10 18%

Euthanised

9 16%

Not known

27 47%

Problems reported at the same time

37 65%

36 63%

34 60%

31 54%

28 49%

25 44%

23 40%

20 35%

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 monocytosis in dogs?: 57 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 4 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).

Monocytosis with similar medicines

Monocytosis after Lufenuron + Milbemycin Oxime (Sentinel) 46 reports · 0.2% of its reports

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