Hyperaesthesia after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 99 reports of hyperaesthesia 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.

99Reports
54%Marked serious
52%Recovered
8.1%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
25 37%
1–2 days
12 18%
3–7 days
4 6.0%
1–4 weeks
5 7.5%
Over a month
21 31%

How the animals did

Recovered
42 42%
Recovered with lasting effects
9 9.1%
Still unwell when reported
17 17%
Died
4 4.0%
Euthanised
4 4.0%
Not known
23 23%

Problems reported at the same time

Age of the animals

Under 1 year
18
1–3 years
38
4–7 years
30
8–11 years
8
12+ years
5

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 hyperaesthesia in dogs?
99 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).

Hyperaesthesia with similar medicines

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