Low platelet count after Milbemycin Oxime + Spinosad (Trifexis) in dogs

159 reports to the FDA describe low platelet count 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, so it is reported less often than average with this medicine.

159Reports
82%Marked serious
33%Recovered
23%Died or euthanised
28 daysTypical onset
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How soon it started

Same day
29 25%
1–2 days
10 8.8%
3–7 days
5 4.4%
1–4 weeks
15 13%
Over a month
55 48%

How the animals did

Recovered
26 16%
Recovered with lasting effects
26 16%
Still unwell when reported
31 19%
Died
16 10%
Euthanised
20 13%
Not known
40 25%

Problems reported at the same time

Age of the animals

Under 1 year
8
1–3 years
48
4–7 years
59
8–11 years
34
12+ years
9

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 low platelet count in dogs?
159 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 28 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).

Low platelet count with similar medicines

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with low platelet count