Disorientation after Selamectin (Revolution) in cats

The FDA has received 114 reports of disorientation in cats after Selamectin. That is 0.5% of all reports for this medicine, compared with 1.0% across reports for all cat medicines, so it is reported less often than average with this medicine.

114Reports
22%Marked serious
11%Recovered
16%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
27 47%
1–2 days
16 28%
3–7 days
10 17%
1–4 weeks
3 5.2%
Over a month
2 3.4%

How the animals did

Recovered
11 9.6%
Recovered with lasting effects
1 0.9%
Still unwell when reported
21 18%
Died
12 11%
Euthanised
6 5.3%
Not known
63 55%

Problems reported at the same time

Age of the animals

Under 1 year
25
1–3 years
21
4–7 years
19
8–11 years
25
12+ years
19

About this medicine

Selamectin prevents heartworm and treats fleas, ear mites and some worms (spot-on).

Products with this ingredient include Revolution. 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 Selamectin cause disorientation in cats?
114 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.
How soon after a dose was it reported?
In half of the reports with dates, it started within 1 day of the first dose.
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).

Disorientation with similar medicines

All reported side effects of Selamectin in cats · Medicines most reported with disorientation