Weight loss after Milbemycin Oxime + Spinosad (Trifexis) in dogs

1,989 reports to the FDA describe weight loss in dogs given Milbemycin Oxime + Spinosad. That is 1.5% of all reports for this medicine, compared with 1.7% across reports for all dog medicines.

1,989Reports

42%Marked serious

33%Recovered

12%Died or euthanised

24 daysTypical onset

How soon it started

Same day

398 34%

1–2 days

78 6.6%

3–7 days

40 3.4%

1–4 weeks

99 8.4%

Over a month

562 48%

How the animals did

Recovered

396 20%

Recovered with lasting effects

257 13%

Still unwell when reported

334 17%

Died

96 4.8%

Euthanised

142 7.1%

Not known

764 38%

Problems reported at the same time

Vomiting

813 41%

Loss of appetite

600 30%

Lethargy

542 27%

Didn't prevent heartworm

338 17%

336 17%

306 15%

238 12%

234 12%

Age of the animals

Under 1 year

122

1–3 years

555

4–7 years

551

8–11 years

432

12+ years

267

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 weight loss in dogs?: 1,989 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 24 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).

Weight loss with similar medicines

Weight loss after Ivermectin + Pyrantel (Heartgard Plus) 889 reports · 0.6% of its reports
Weight loss after Moxidectin (ProHeart 6) 858 reports · 1.7% of its reports
Weight loss after Milbemycin Oxime + Praziquantel (Interceptor Plus) 515 reports · 1.6% of its reports
Weight loss after Milbemycin Oxime (Interceptor) 348 reports · 1.2% of its reports
Weight loss after Selamectin (Revolution) 230 reports · 0.8% of its reports
Weight loss after Ivermectin (Heartgard) 200 reports · 1.7% of its reports
Weight loss after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 42 reports · 0.5% of its reports
Weight loss after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 29 reports · 2.5% of its reports

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