Excessive licking and/or grooming after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 88 reports of excessive licking and/or grooming 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, so it is reported less often than average with this medicine.

88Reports

23%Marked serious

33%Recovered

4.5%Died or euthanised

Same dayTypical onset

How soon it started

Same day

30 53%

1–2 days

4 7.0%

3–7 days

2 3.5%

1–4 weeks

7 12%

Over a month

14 25%

How the animals did

Recovered

16 18%

Recovered with lasting effects

13 15%

Still unwell when reported

18 20%

Died

1 1.1%

Euthanised

3 3.4%

Not known

37 42%

Problems reported at the same time

Itching

28 32%

Vomiting

22 25%

Lethargy

21 24%

Skin rash or irritation

18 20%

Behaviour change

13 15%

Loss of appetite

11 13%

Reddening of the skin

9 10%

Didn't work as expected

7 8.0%

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 excessive licking and/or grooming in dogs?: 88 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 the same 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).

Excessive licking and/or grooming with similar medicines

Excessive licking and/or grooming after Ivermectin + Pyrantel (Heartgard Plus) 80 reports · 0.1% of its reports
Excessive licking and/or grooming after Moxidectin (ProHeart 6) 27 reports · 0.1% of its reports
Excessive licking and/or grooming after Milbemycin Oxime (Interceptor) 30 reports · 0.1% of its reports
Excessive licking and/or grooming after Selamectin (Revolution) 51 reports · 0.2% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with excessive licking and/or grooming