Nystagmus after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 122 reports of nystagmus in dogs after Milbemycin Oxime + 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.

122Reports

69%Marked serious

39%Recovered

18%Died or euthanised

6 daysTypical onset

How soon it started

Same day

27 29%

1–2 days

12 13%

3–7 days

11 12%

1–4 weeks

8 8.7%

Over a month

34 37%

How the animals did

Recovered

30 25%

Recovered with lasting effects

17 14%

Still unwell when reported

23 19%

Died

8 6.6%

Euthanised

14 11%

Not known

30 25%

Problems reported at the same time

52 43%

51 42%

40 33%

34 28%

Head tilt - ear disorder

31 25%

Loss of appetite

26 21%

Seizures

25 20%

Death

22 18%

Age of the animals

Under 1 year

1–3 years

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 nystagmus in dogs?: 122 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 6 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).

Nystagmus with similar medicines

Nystagmus after Ivermectin + Pyrantel (Heartgard Plus) 88 reports · 0.1% of its reports
Nystagmus after Moxidectin (ProHeart 6) 105 reports · 0.2% of its reports
Nystagmus after Milbemycin Oxime + Praziquantel (Interceptor Plus) 41 reports · 0.1% of its reports
Nystagmus after Milbemycin Oxime (Interceptor) 42 reports · 0.1% of its reports
Nystagmus after Selamectin (Revolution) 52 reports · 0.2% of its reports
Nystagmus after Ivermectin (Heartgard) 48 reports · 0.4% of its reports

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