Overdose after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 2,052 reports of overdose in dogs after Milbemycin Oxime + Spinosad. That is 1.6% of all reports for this medicine, compared with 1.3% across reports for all dog medicines.

2,052Reports

11%Marked serious

45%Recovered

1.2%Died or euthanised

Same dayTypical onset

How soon it started

Same day

428 51%

1–2 days

125 15%

3–7 days

18 2.2%

1–4 weeks

38 4.6%

Over a month

223 27%

How the animals did

Recovered

877 43%

Recovered with lasting effects

50 2.4%

Still unwell when reported

375 18%

Died

12 0.6%

Euthanised

12 0.6%

Not known

726 35%

Problems reported at the same time

946 46%

841 41%

835 41%

334 16%

270 13%

Didn't prevent heartworm

175 8.5%

Wobbliness (ataxia)

136 6.6%

Diarrhea

109 5.3%

Age of the animals

Under 1 year

488

1–3 years

673

4–7 years

400

8–11 years

257

12+ years

135

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 overdose in dogs?: 2,052 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).

Overdose with similar medicines

Overdose after Ivermectin + Pyrantel (Heartgard Plus) 1,647 reports · 1.1% of its reports
Overdose after Moxidectin (ProHeart 6) 366 reports · 0.7% of its reports
Overdose after Milbemycin Oxime + Praziquantel (Interceptor Plus) 266 reports · 0.8% of its reports
Overdose after Milbemycin Oxime (Interceptor) 131 reports · 0.4% of its reports
Overdose after Selamectin (Revolution) 160 reports · 0.5% of its reports
Overdose after Ivermectin (Heartgard) 134 reports · 1.1% of its reports
Overdose after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 185 reports · 2.2% of its reports
Overdose after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 31 reports · 2.7% of its reports

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