Tooth disorder after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 168 reports of tooth disorder 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, so it is reported unusually often with this medicine.

168Reports
57%Marked serious
43%Recovered
14%Died or euthanised
83 daysTypical onset
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How soon it started

Same day
20 19%
1–2 days
10 9.3%
3–7 days
4 3.7%
1–4 weeks
7 6.5%
Over a month
67 62%

How the animals did

Recovered
27 16%
Recovered with lasting effects
46 27%
Still unwell when reported
28 17%
Died
8 4.8%
Euthanised
15 8.9%
Not known
44 26%

Problems reported at the same time

Age of the animals

Under 1 year
15
1–3 years
33
4–7 years
46
8–11 years
52
12+ years
21

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 tooth disorder in dogs?
168 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 83 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).

Tooth disorder with similar medicines

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