Bacterial skin infection after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 180 reports of bacterial skin infection 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.

180Reports

28%Marked serious

33%Recovered

3.9%Died or euthanised

37 daysTypical onset

How soon it started

Same day

32 28%

1–2 days

2 1.8%

3–7 days

7 6.1%

1–4 weeks

12 11%

Over a month

61 54%

How the animals did

Recovered

33 18%

Recovered with lasting effects

26 14%

Still unwell when reported

57 32%

Died

5 2.8%

Euthanised

2 1.1%

Not known

57 32%

Problems reported at the same time

Itching

60 33%

Vomiting

59 33%

Skin rash or irritation

31 17%

Hair loss

27 15%

Didn't work as expected

22 12%

Diarrhea

19 11%

Skin disorders

19 11%

Didn't stop fleas

19 11%

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 bacterial skin infection in dogs?: 180 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 37 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).

Bacterial skin infection with similar medicines

Bacterial skin infection after Ivermectin + Pyrantel (Heartgard Plus) 51 reports · 0.0% of its reports
Bacterial skin infection after Moxidectin (ProHeart 6) 25 reports · 0.0% of its reports
Bacterial skin infection after Milbemycin Oxime + Praziquantel (Interceptor Plus) 40 reports · 0.1% of its reports
Bacterial skin infection after Selamectin (Revolution) 22 reports · 0.1% of its reports
Bacterial skin infection after Ivermectin (Heartgard) 27 reports · 0.2% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with bacterial skin infection