Red eye after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 94 reports of red eye 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.

94Reports
26%Marked serious
53%Recovered
4.3%Died or euthanised
Same dayTypical onset
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How soon it started

Same day
44 60%
1–2 days
4 5.5%
3–7 days
1 1.4%
1–4 weeks
3 4.1%
Over a month
21 29%

How the animals did

Recovered
43 46%
Recovered with lasting effects
7 7.4%
Still unwell when reported
14 15%
Died
4 4.3%
Not known
26 28%

Problems reported at the same time

Age of the animals

Under 1 year
20
1–3 years
45
4–7 years
20
8–11 years
5
12+ years
1

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 red eye in dogs?
94 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 the same 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).

Red eye with similar medicines

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