Death after Milbemycin Oxime (Interceptor) in cats

20 reports to the FDA describe death in cats given Milbemycin Oxime. That is 4.9% of all reports for this medicine, compared with 8.9% across reports for all cat medicines, so it is reported less often than average with this medicine.

20Reports
45%Marked serious
0.0%Recovered
95%Died or euthanised
–Typical onset
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How the animals did

Died
13 65%
Euthanised
6 30%
Not known
1 5.0%

Problems reported at the same time

Pale mucous membrane
4 20%
Kidney problems
4 20%
Swelling
3 15%
Pain
2 10%
Weakness
2 10%

Age of the animals

Under 1 year
9
1–3 years
2
4–7 years
2
8–11 years
3
12+ years
2

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.

Questions owners ask

Can Milbemycin Oxime cause death in cats?
20 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.
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).

Death with similar medicines

All reported side effects of Milbemycin Oxime in cats · Medicines most reported with death