Didn't stop worms after Selamectin (Revolution) in cats

574 reports to the FDA describe didn't stop worms in cats given Selamectin. That is 2.6% of all reports for this medicine, compared with 1.8% across reports for all cat medicines.

574Reports

13%Marked serious

3.1%Recovered

0.5%Died or euthanised

28 daysTypical onset

How soon it started

Same day

32 12%

1–2 days

9 3.5%

3–7 days

19 7.4%

1–4 weeks

83 32%

Over a month

115 45%

How the animals did

Recovered

18 3.1%

Still unwell when reported

170 30%

Died

2 0.3%

Euthanised

1 0.2%

Not known

383 67%

Problems reported at the same time

Didn't stop fleas

88 15%

Didn't work as expected

52 9.1%

Drug dose administration interval too short

19 3.3%

16 2.8%

15 2.6%

14 2.4%

12 2.1%

10 1.7%

Age of the animals

Under 1 year

181

1–3 years

145

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 didn't stop worms in cats?: 574 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 28 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).

Didn't stop worms with similar medicines

Didn't stop worms after Eprinomectin + Esafoxolaner + Praziquantel (NexGard Combo) 357 reports · 11% of its reports
Didn't stop worms after Eprinomectin + Praziquantel 99 reports · 17% of its reports

All reported side effects of Selamectin in cats · Medicines most reported with didn't stop worms