General illness after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 339 reports of general illness in dogs after Milbemycin Oxime + Spinosad. That is 0.3% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

339Reports
32%Marked serious
42%Recovered
13%Died or euthanised
Same dayTypical onset
SponsoredWorried about your pet? Ask a veterinarian online, 24/7

How soon it started

Same day
153 59%
1–2 days
19 7.3%
3–7 days
6 2.3%
1–4 weeks
13 5.0%
Over a month
69 27%

How the animals did

Recovered
110 32%
Recovered with lasting effects
31 9.1%
Still unwell when reported
26 7.7%
Died
26 7.7%
Euthanised
17 5.0%
Not known
129 38%

Problems reported at the same time

Age of the animals

Under 1 year
22
1–3 years
83
4–7 years
67
8–11 years
45
12+ years
34

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 general illness in dogs?
339 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).

General illness with similar medicines

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