Skin lump after Milbemycin Oxime + Spinosad (Trifexis) in dogs

92 reports to the FDA describe skin lump in dogs given 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 less often than average with this medicine.

92Reports
46%Marked serious
37%Recovered
8.7%Died or euthanised
26 daysTypical onset
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How soon it started

Same day
17 31%
1–2 days
3 5.5%
3–7 days
2 3.6%
1–4 weeks
6 11%
Over a month
27 49%

How the animals did

Recovered
19 21%
Recovered with lasting effects
15 16%
Still unwell when reported
17 18%
Died
3 3.3%
Euthanised
5 5.4%
Not known
33 36%

Problems reported at the same time

Age of the animals

Under 1 year
5
1–3 years
22
4–7 years
19
8–11 years
33
12+ years
8

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 skin lump in dogs?
92 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 26 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).

Skin lump with similar medicines

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