Weight loss after Selamectin (Revolution) in cats

522 reports to the FDA describe weight loss in cats given Selamectin. That is 2.4% of all reports for this medicine, compared with 4.6% across reports for all cat medicines, so it is reported less often than average with this medicine.

522Reports
26%Marked serious
6.7%Recovered
20%Died or euthanised
2 daysTypical onset
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How soon it started

Same day
75 29%
1–2 days
61 24%
3–7 days
41 16%
1–4 weeks
36 14%
Over a month
43 17%

How the animals did

Recovered
33 6.3%
Recovered with lasting effects
2 0.4%
Still unwell when reported
130 25%
Died
78 15%
Euthanised
27 5.2%
Not known
252 48%

Problems reported at the same time

Age of the animals

Under 1 year
84
1–3 years
86
4–7 years
110
8–11 years
114
12+ years
106

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 weight loss in cats?
522 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 2 days 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).

Weight loss with similar medicines

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