Behaviour change after Milbemycin Oxime + Spinosad (Trifexis) in dogs

4,099 reports to the FDA describe behaviour change in dogs given Milbemycin Oxime + Spinosad. That is 3.2% of all reports for this medicine, compared with 2.5% across reports for all dog medicines.

4,099Reports

29%Marked serious

60%Recovered

6.1%Died or euthanised

1 daysTypical onset

How soon it started

Same day

1,537 49%

1–2 days

322 10%

3–7 days

113 3.6%

1–4 weeks

169 5.3%

Over a month

1,025 32%

How the animals did

Recovered

1,976 48%

Recovered with lasting effects

480 12%

Still unwell when reported

465 11%

Died

122 3.0%

Euthanised

128 3.1%

Not known

928 23%

Problems reported at the same time

1,855 45%

1,264 31%

879 21%

871 21%

433 11%

370 9.0%

359 8.8%

351 8.6%

Age of the animals

Under 1 year

567

1–3 years

1,509

4–7 years

1,061

8–11 years

579

12+ years

227

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 behaviour change in dogs?: 4,099 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 1 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).

Behaviour change with similar medicines

Behaviour change after Ivermectin + Pyrantel (Heartgard Plus) 1,674 reports · 1.1% of its reports
Behaviour change after Moxidectin (ProHeart 6) 688 reports · 1.4% of its reports
Behaviour change after Milbemycin Oxime + Praziquantel (Interceptor Plus) 852 reports · 2.7% of its reports
Behaviour change after Milbemycin Oxime (Interceptor) 364 reports · 1.2% of its reports
Behaviour change after Selamectin (Revolution) 652 reports · 2.2% of its reports
Behaviour change after Ivermectin (Heartgard) 368 reports · 3.1% of its reports
Behaviour change after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 146 reports · 1.7% of its reports
Behaviour change after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 55 reports · 4.7% of its reports

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