Respiratory tract disorder after Milbemycin Oxime + Spinosad (Trifexis) in dogs

67 reports to the FDA describe respiratory tract disorder in dogs given Milbemycin Oxime + Spinosad. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

67Reports
72%Marked serious
25%Recovered
45%Died or euthanised
19 daysTypical onset
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How soon it started

Same day
14 30%
1–2 days
4 8.7%
3–7 days
1 2.2%
1–4 weeks
7 15%
Over a month
20 43%

How the animals did

Recovered
14 21%
Recovered with lasting effects
3 4.5%
Still unwell when reported
8 12%
Died
19 28%
Euthanised
11 16%
Not known
12 18%

Problems reported at the same time

Age of the animals

Under 1 year
9
1–3 years
12
4–7 years
22
8–11 years
13
12+ years
9

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 respiratory tract disorder in dogs?
67 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 19 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).

Respiratory tract disorder with similar medicines

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with respiratory tract disorder