Stiffness after Milbemycin Oxime + Spinosad (Trifexis) in dogs

182 reports to the FDA describe stiffness in dogs given Milbemycin Oxime + Spinosad. That is 0.1% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

182Reports
41%Marked serious
66%Recovered
9.3%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
60 48%
1–2 days
11 8.9%
3–7 days
2 1.6%
1–4 weeks
8 6.5%
Over a month
43 35%

How the animals did

Recovered
99 54%
Recovered with lasting effects
22 12%
Still unwell when reported
20 11%
Died
10 5.5%
Euthanised
7 3.8%
Not known
24 13%

Problems reported at the same time

Age of the animals

Under 1 year
19
1–3 years
72
4–7 years
42
8–11 years
33
12+ years
11

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 stiffness in dogs?
182 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 1 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).

Stiffness with similar medicines

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