Milbemycin Oxime + Spinosad (Trifexis) side effects in dogs
129,736 reports sent to the FDA between 2009 and 2026 involve Milbemycin Oxime + Spinosad in dogs. The most reported problems were vomiting, lethargy, loss of appetite. 12% were marked serious, and where it was recorded, signs eased after stopping the medicine in 55% of cases.
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.
Most reported side effects
Share = percentage of this medicine's reports that mention the problem. One report can list several problems.
Reports that it didn't work
Some reports are about the medicine not working (for example a dog still getting fleas or heartworm), not about a side effect.
How soon problems started
Time from the first dose to the first sign, where both dates were reported (90,606 reports).
How the animals did
Breeds named most often
Popular breeds appear more often because there are more of them.
- Labrador Retriever 9,614 reports
- Yorkshire Terrier 4,221 reports
- Chihuahua 4,014 reports
- Shih Tzu 3,795 reports
- German Shepherd Dog 3,726 reports
- Boxer (german Boxer) 3,677 reports
- Golden Retriever 3,234 reports
- Pit Bull 2,689 reports
- Dachshund 2,148 reports
- Australian Shepherd Dog 2,079 reports