Blood problems after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 735 reports of blood problems in dogs after Milbemycin Oxime + Spinosad. That is 0.6% of all reports for this medicine, compared with 1.8% across reports for all dog medicines, so it is reported less often than average with this medicine.

735Reports

87%Marked serious

29%Recovered

29%Died or euthanised

30 daysTypical onset

How soon it started

Same day

108 21%

1–2 days

67 13%

3–7 days

25 4.9%

1–4 weeks

57 11%

Over a month

249 49%

How the animals did

Recovered

104 14%

Recovered with lasting effects

110 15%

Still unwell when reported

153 21%

Died

83 11%

Euthanised

132 18%

Not known

153 21%

Problems reported at the same time

372 51%

297 40%

262 36%

243 33%

213 29%

151 21%

137 19%

127 17%

Age of the animals

Under 1 year

1–3 years

140

4–7 years

223

8–11 years

201

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 blood problems in dogs?: 735 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 30 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).

Blood problems with similar medicines

Blood problems after Ivermectin + Pyrantel (Heartgard Plus) 545 reports · 0.4% of its reports
Blood problems after Moxidectin (ProHeart 6) 1,343 reports · 2.7% of its reports
Blood problems after Milbemycin Oxime + Praziquantel (Interceptor Plus) 225 reports · 0.7% of its reports
Blood problems after Milbemycin Oxime (Interceptor) 251 reports · 0.8% of its reports
Blood problems after Selamectin (Revolution) 327 reports · 1.1% of its reports
Blood problems after Ivermectin (Heartgard) 145 reports · 1.2% of its reports
Blood problems after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 37 reports · 0.4% of its reports
Blood problems after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 30 reports · 2.6% of its reports

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