Loose stool after Selamectin (Revolution) in cats

The FDA has received 81 reports of loose stool in cats after Selamectin. That is 0.4% of all reports for this medicine, compared with 0.5% across reports for all cat medicines.

81Reports

8.6%Marked serious

8.6%Recovered

2.5%Died or euthanised

1 daysTypical onset

How soon it started

Same day

14 44%

1–2 days

7 22%

3–7 days

7 22%

1–4 weeks

1 3.1%

Over a month

3 9.4%

How the animals did

Recovered

7 8.6%

Still unwell when reported

13 16%

Died

2 2.5%

Not known

59 73%

Problems reported at the same time

28 35%

23 28%

21 26%

13 16%

8 9.9%

6 7.4%

6 7.4%

6 7.4%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

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 loose stool in cats?: 81 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).

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