Conjunctivitis after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 104 reports of conjunctivitis in dogs after Milbemycin Oxime + Spinosad. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

104Reports

41%Marked serious

41%Recovered

6.7%Died or euthanised

75 daysTypical onset

How soon it started

Same day

12 16%

1–2 days

3 4.1%

3–7 days

1 1.4%

1–4 weeks

8 11%

Over a month

49 67%

How the animals did

Recovered

31 30%

Recovered with lasting effects

12 12%

Still unwell when reported

21 20%

Died

3 2.9%

Euthanised

4 3.8%

Not known

33 32%

Problems reported at the same time

Vomiting

35 34%

Lethargy

22 21%

Didn't prevent heartworm

21 20%

Loss of appetite

15 14%

Skin rash or irritation

14 13%

Ocular discharge

13 13%

Diarrhea

13 13%

Didn't work as expected

11 11%

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 conjunctivitis in dogs?: 104 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 75 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).

Conjunctivitis with similar medicines

Conjunctivitis after Ivermectin + Pyrantel (Heartgard Plus) 31 reports · 0.0% of its reports
Conjunctivitis after Moxidectin (ProHeart 6) 50 reports · 0.1% of its reports
Conjunctivitis after Milbemycin Oxime + Praziquantel (Interceptor Plus) 39 reports · 0.1% of its reports
Conjunctivitis after Milbemycin Oxime (Interceptor) 22 reports · 0.1% of its reports
Conjunctivitis after Selamectin (Revolution) 26 reports · 0.1% of its reports

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