Bone and joint disorder after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 189 reports of bone and joint disorder 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.

189Reports

78%Marked serious

33%Recovered

17%Died or euthanised

38 daysTypical onset

How soon it started

Same day

38 34%

1–2 days

7 6.3%

3–7 days

1 0.9%

1–4 weeks

7 6.3%

Over a month

58 52%

How the animals did

Recovered

18 9.5%

Recovered with lasting effects

45 24%

Still unwell when reported

45 24%

Died

15 7.9%

Euthanised

17 9.0%

Not known

49 26%

Problems reported at the same time

Vomiting

67 35%

Lethargy

42 22%

Didn't prevent heartworm

34 18%

Loss of appetite

33 17%

Death

31 16%

Abnormal radiograph finding

30 16%

Liver problems

28 15%

Behaviour change

27 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 bone and joint disorder in dogs?: 189 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 38 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).

Bone and joint disorder with similar medicines

Bone and joint disorder after Ivermectin + Pyrantel (Heartgard Plus) 33 reports · 0.0% of its reports
Bone and joint disorder after Moxidectin (ProHeart 6) 23 reports · 0.0% of its reports
Bone and joint disorder after Milbemycin Oxime + Praziquantel (Interceptor Plus) 58 reports · 0.2% of its reports
Bone and joint disorder after Milbemycin Oxime (Interceptor) 29 reports · 0.1% of its reports
Bone and joint disorder after Ivermectin (Heartgard) 29 reports · 0.2% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with bone and joint disorder