Splenic neoplasm after Milbemycin Oxime + Spinosad (Trifexis) in dogs

52 reports to the FDA describe splenic neoplasm in dogs given Milbemycin Oxime + Spinosad. That is 0.0% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported less often than average with this medicine.

52Reports
98%Marked serious
15%Recovered
77%Died or euthanised
111 daysTypical onset
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How soon it started

Same day
8 24%
1–2 days
3 9.1%
3–7 days
0 0.0%
1–4 weeks
2 6.1%
Over a month
20 61%

How the animals did

Recovered
1 1.9%
Recovered with lasting effects
7 13%
Still unwell when reported
2 3.8%
Died
10 19%
Euthanised
30 58%
Not known
2 3.8%

Problems reported at the same time

Age of the animals

Under 1 year
0
1–3 years
1
4–7 years
11
8–11 years
30
12+ years
6

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 splenic neoplasm in dogs?
52 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 111 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).

Splenic neoplasm with similar medicines

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