Allergy after Milbemycin Oxime + Spinosad (Trifexis) in dogs

473 reports to the FDA describe allergy in dogs given Milbemycin Oxime + Spinosad. That is 0.4% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported unusually often with this medicine.

473Reports
15%Marked serious
22%Recovered
2.1%Died or euthanised
57 daysTypical onset
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How soon it started

Same day
81 34%
1–2 days
6 2.5%
3–7 days
1 0.4%
1–4 weeks
17 7.2%
Over a month
131 56%

How the animals did

Recovered
57 12%
Recovered with lasting effects
47 9.9%
Still unwell when reported
171 36%
Died
5 1.1%
Euthanised
5 1.1%
Not known
188 40%

Problems reported at the same time

Age of the animals

Under 1 year
38
1–3 years
172
4–7 years
139
8–11 years
83
12+ years
19

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 allergy in dogs?
473 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 57 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).

Allergy with similar medicines

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