Neurological signs after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 325 reports of neurological signs in dogs after Milbemycin Oxime + Spinosad. That is 0.3% of all reports for this medicine, compared with 0.3% across reports for all dog medicines.

325Reports

55%Marked serious

59%Recovered

11%Died or euthanised

1 daysTypical onset

How soon it started

Same day

110 46%

1–2 days

27 11%

3–7 days

11 4.6%

1–4 weeks

15 6.2%

Over a month

78 32%

How the animals did

Recovered

153 47%

Recovered with lasting effects

40 12%

Still unwell when reported

40 12%

Died

11 3.4%

Euthanised

24 7.4%

Not known

57 18%

Problems reported at the same time

127 39%

95 29%

90 28%

85 26%

76 23%

70 22%

58 18%

47 14%

Age of the animals

Under 1 year

1–3 years

104

4–7 years

8–11 years

12+ years

About this medicine

Milbemycin Oxime prevents heartworm and controls some intestinal worms (monthly). Spinosad kills fleas; monthly chewable.

Products with this combination include Trifexis. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Some herding breeds (for example Collies) carry the MDR1 gene variant and can be more sensitive to this drug class at high doses.

Questions owners ask

Can Milbemycin Oxime + Spinosad cause neurological signs in dogs?: 325 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 1 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).

Neurological signs with similar medicines

Neurological signs after Ivermectin + Pyrantel (Heartgard Plus) 165 reports · 0.1% of its reports
Neurological signs after Moxidectin (ProHeart 6) 139 reports · 0.3% of its reports
Neurological signs after Milbemycin Oxime + Praziquantel (Interceptor Plus) 41 reports · 0.1% of its reports
Neurological signs after Milbemycin Oxime (Interceptor) 39 reports · 0.1% of its reports
Neurological signs after Selamectin (Revolution) 69 reports · 0.2% of its reports
Neurological signs after Ivermectin (Heartgard) 86 reports · 0.7% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with neurological signs