Milbemycin Oxime (Interceptor) side effects in cats
405 reports sent to the FDA between 1995 and 2026 involve Milbemycin Oxime in cats. The most reported problems were lethargy, vomiting, wobbliness (ataxia). 13% were marked serious, and where it was recorded, signs eased after stopping the medicine in 5% of cases.
About this medicine
Milbemycin Oxime prevents heartworm and controls some intestinal worms (monthly).
Products with this ingredient include Interceptor. 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 cat 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 (153 reports).
How the animals did
Breeds named most often
Popular breeds appear more often because there are more of them.
- Domestic 145 reports
- Domestic Shorthair 145 reports
- Domestic Longhair 23 reports
- Domestic Mediumhair 12 reports
- Siamese 6 reports
- Maine Coon 5 reports
- Ragdoll 3 reports
- Sphynx 2 reports
- Himalayan 1 reports
- Burmese 1 reports