Labelled drug-drug interaction medication error after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 121 reports of labelled drug-drug interaction medication error in dogs after Milbemycin Oxime + Spinosad. That is 0.1% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported less often than average with this medicine.

121Reports
71%Marked serious
60%Recovered
8.3%Died or euthanised
33 daysTypical onset
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How soon it started

Same day
7 8.2%
1–2 days
8 9.4%
3–7 days
4 4.7%
1–4 weeks
18 21%
Over a month
48 56%

How the animals did

Recovered
64 53%
Recovered with lasting effects
8 6.6%
Still unwell when reported
9 7.4%
Died
8 6.6%
Euthanised
2 1.7%
Not known
30 25%

Problems reported at the same time

Age of the animals

Under 1 year
52
1–3 years
48
4–7 years
8
8–11 years
6
12+ years
2

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 labelled drug-drug interaction medication error in dogs?
121 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 33 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).

Labelled drug-drug interaction medication error with similar medicines

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with labelled drug-drug interaction medication error