Constipation after Milbemycin Oxime + Spinosad (Trifexis) in dogs

152 reports to the FDA describe constipation 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.

152Reports

38%Marked serious

46%Recovered

11%Died or euthanised

2 daysTypical onset

How soon it started

Same day

45 40%

1–2 days

14 13%

3–7 days

10 8.9%

1–4 weeks

11 9.8%

Over a month

32 29%

How the animals did

Recovered

47 31%

Recovered with lasting effects

23 15%

Still unwell when reported

25 16%

Died

8 5.3%

Euthanised

8 5.3%

Not known

41 27%

Problems reported at the same time

73 48%

73 48%

63 41%

27 18%

19 13%

18 12%

Abnormal radiograph finding

17 11%

Liver problems

15 9.9%

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 constipation in dogs?: 152 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 2 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).

Constipation with similar medicines

Constipation after Ivermectin + Pyrantel (Heartgard Plus) 105 reports · 0.1% of its reports
Constipation after Moxidectin (ProHeart 6) 33 reports · 0.1% of its reports
Constipation after Milbemycin Oxime + Praziquantel (Interceptor Plus) 42 reports · 0.1% of its reports
Constipation after Milbemycin Oxime (Interceptor) 24 reports · 0.1% of its reports
Constipation after Selamectin (Revolution) 33 reports · 0.1% of its reports

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