Inappropriate defecation after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 198 reports of inappropriate defecation in dogs after Milbemycin Oxime + Spinosad. That is 0.2% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

198Reports

44%Marked serious

54%Recovered

12%Died or euthanised

1 daysTypical onset

How soon it started

Same day

64 43%

1–2 days

16 11%

3–7 days

8 5.4%

1–4 weeks

15 10%

Over a month

46 31%

How the animals did

Recovered

79 40%

Recovered with lasting effects

28 14%

Still unwell when reported

25 13%

Died

12 6.1%

Euthanised

11 5.6%

Not known

43 22%

Problems reported at the same time

Vomiting

90 45%

Lethargy

74 37%

Inappropriate urination

65 33%

51 26%

48 24%

39 20%

28 14%

28 14%

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 inappropriate defecation in dogs?: 198 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).

Inappropriate defecation with similar medicines

Inappropriate defecation after Ivermectin + Pyrantel (Heartgard Plus) 217 reports · 0.1% of its reports
Inappropriate defecation after Moxidectin (ProHeart 6) 119 reports · 0.2% of its reports
Inappropriate defecation after Milbemycin Oxime + Praziquantel (Interceptor Plus) 83 reports · 0.3% of its reports
Inappropriate defecation after Ivermectin (Heartgard) 26 reports · 0.2% of its reports
Inappropriate defecation after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 46 reports · 0.5% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with inappropriate defecation