Blood and lymphatic system disorder after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 85 reports of blood and lymphatic system disorder in dogs after Milbemycin Oxime + Spinosad. That is 0.1% of all reports for this medicine, compared with 0.0% across reports for all dog medicines.

85Reports
80%Marked serious
40%Recovered
29%Died or euthanised
31 daysTypical onset
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How soon it started

Same day
19 28%
1–2 days
5 7.2%
3–7 days
2 2.9%
1–4 weeks
7 10%
Over a month
36 52%

How the animals did

Recovered
14 16%
Recovered with lasting effects
20 24%
Still unwell when reported
14 16%
Died
13 15%
Euthanised
12 14%
Not known
12 14%

Problems reported at the same time

Age of the animals

Under 1 year
9
1–3 years
22
4–7 years
24
8–11 years
23
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 blood and lymphatic system disorder in dogs?
85 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 31 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).

Blood and lymphatic system disorder with similar medicines

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with blood and lymphatic system disorder