Moxidectin (ProHeart 6) side effects in horses
1,369 reports sent to the FDA between 1997 and 2026 involve Moxidectin in horses. The most reported problems were locking mechanism abnormal, wobbliness (ataxia), lethargy. 4.0% were marked serious, and where it was recorded, signs eased after stopping the medicine in 0% of cases.
About this medicine
Moxidectin prevents heartworm disease (monthly topical, or a 6- or 12-month injection for dogs).
Products with this ingredient include ProHeart 6, ProHeart 12. 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 horse 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 (100 reports).
How the animals did
Breeds named most often
Popular breeds appear more often because there are more of them.
- Quarter Horse 392 reports
- Horse 308 reports
- Miniature 119 reports
- Thoroughbred 85 reports
- Paint 64 reports
- Arab 53 reports
- Horse (other) 50 reports
- Tennessee Walking Horse 35 reports
- Appaloosa 25 reports
- Morgan 22 reports