Lameness after Milbemycin Oxime + Spinosad (Trifexis) in dogs

452 reports to the FDA describe lameness in dogs given Milbemycin Oxime + Spinosad. That is 0.3% of all reports for this medicine, compared with 0.6% across reports for all dog medicines, so it is reported less often than average with this medicine.

452Reports

46%Marked serious

32%Recovered

10%Died or euthanised

32 daysTypical onset

How soon it started

Same day

70 25%

1–2 days

22 7.7%

3–7 days

13 4.6%

1–4 weeks

29 10%

Over a month

151 53%

How the animals did

Recovered

88 19%

Recovered with lasting effects

57 13%

Still unwell when reported

105 23%

Died

22 4.9%

Euthanised

25 5.5%

Not known

155 34%

Problems reported at the same time

Vomiting

152 34%

Lethargy

151 33%

Loss of appetite

95 21%

Didn't prevent heartworm

78 17%

Behaviour change

59 13%

Diarrhea

53 12%

Didn't work as expected

46 10%

Death

44 9.7%

Age of the animals

Under 1 year

1–3 years

135

4–7 years

112

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 lameness in dogs?: 452 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 32 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).

Lameness with similar medicines

Lameness after Ivermectin + Pyrantel (Heartgard Plus) 319 reports · 0.2% of its reports
Lameness after Moxidectin (ProHeart 6) 363 reports · 0.7% of its reports
Lameness after Milbemycin Oxime + Praziquantel (Interceptor Plus) 233 reports · 0.7% of its reports
Lameness after Milbemycin Oxime (Interceptor) 115 reports · 0.4% of its reports
Lameness after Selamectin (Revolution) 100 reports · 0.3% of its reports
Lameness after Ivermectin (Heartgard) 59 reports · 0.5% of its reports

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