Abnormal stool colouration after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 125 reports of abnormal stool colouration in dogs after Milbemycin Oxime + Spinosad. That is 0.1% of all reports for this medicine, compared with 0.1% across reports for all dog medicines.

125Reports

43%Marked serious

46%Recovered

14%Died or euthanised

1 daysTypical onset

How soon it started

Same day

40 42%

1–2 days

17 18%

3–7 days

2 2.1%

1–4 weeks

3 3.2%

Over a month

33 35%

How the animals did

Recovered

43 34%

Recovered with lasting effects

15 12%

Still unwell when reported

19 15%

Died

12 9.6%

Euthanised

5 4.0%

Not known

31 25%

Problems reported at the same time

69 55%

56 45%

56 45%

51 41%

28 22%

26 21%

16 13%

16 13%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

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 abnormal stool colouration in dogs?: 125 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 1 day 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).

Abnormal stool colouration with similar medicines

Abnormal stool colouration after Ivermectin + Pyrantel (Heartgard Plus) 110 reports · 0.1% of its reports
Abnormal stool colouration after Moxidectin (ProHeart 6) 39 reports · 0.1% of its reports
Abnormal stool colouration after Milbemycin Oxime + Praziquantel (Interceptor Plus) 36 reports · 0.1% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with abnormal stool colouration