Nausea after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 876 reports of nausea in dogs after Milbemycin Oxime + Spinosad. That is 0.7% of all reports for this medicine, compared with 0.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

876Reports
18%Marked serious
69%Recovered
2.9%Died or euthanised
Same dayTypical onset
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How soon it started

Same day
434 63%
1–2 days
46 6.7%
3–7 days
8 1.2%
1–4 weeks
24 3.5%
Over a month
177 26%

How the animals did

Recovered
530 61%
Recovered with lasting effects
76 8.7%
Still unwell when reported
79 9.0%
Died
16 1.8%
Euthanised
9 1.0%
Not known
166 19%

Problems reported at the same time

Age of the animals

Under 1 year
115
1–3 years
290
4–7 years
236
8–11 years
136
12+ years
48

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 nausea in dogs?
876 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).

Nausea with similar medicines

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