Ivermectin (Heartgard) side effects in dogs
12,017 reports sent to the FDA between 1995 and 2026 involve Ivermectin in dogs. The most reported problems were vomiting, lethargy, wobbliness (ataxia). 27% were marked serious, and where it was recorded, signs eased after stopping the medicine in 55% of cases.
About this medicine
Ivermectin prevents heartworm disease (monthly).
Products with this ingredient include Heartgard. 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 (5,454 reports).
How the animals did
Breeds named most often
Popular breeds appear more often because there are more of them.
- Labrador Retriever 1,096 reports
- German Shepherd Dog 426 reports
- Yorkshire Terrier 303 reports
- Chihuahua 301 reports
- Golden Retriever 279 reports
- Boxer (german Boxer) 263 reports
- Shih Tzu 248 reports
- Australian Shepherd Dog 228 reports
- Pit Bull 228 reports
- Beagle 194 reports