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

The FDA has received 2,317 reports of didn't stop worms in dogs after Selamectin. That is 7.9% of all reports for this medicine, compared with 8.4% across reports for all dog medicines.

2,317Reports

7.2%Marked serious

1.0%Recovered

0.4%Died or euthanised

112 daysTypical onset

How soon it started

Same day

38 8.6%

1–2 days

5 1.1%

3–7 days

7 1.6%

1–4 weeks

48 11%

Over a month

344 78%

How the animals did

Recovered

24 1.0%

Still unwell when reported

616 27%

Died

10 0.4%

Not known

1,667 72%

Problems reported at the same time

Didn't work as expected

291 13%

Didn't prevent heartworm

156 6.7%

98 4.2%

59 2.5%

56 2.4%

36 1.6%

24 1.0%

24 1.0%

Age of the animals

Under 1 year

294

1–3 years

864

4–7 years

546

8–11 years

297

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 dogs?: 2,317 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 112 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 Ivermectin + Pyrantel (Heartgard Plus) 32,467 reports · 22% of its reports
Didn't stop worms after Milbemycin Oxime + Spinosad (Trifexis) 4,483 reports · 3.5% of its reports
Didn't stop worms after Moxidectin (ProHeart 6) 9,537 reports · 19% of its reports
Didn't stop worms after Milbemycin Oxime + Praziquantel (Interceptor Plus) 6,097 reports · 19% of its reports
Didn't stop worms after Milbemycin Oxime (Interceptor) 4,308 reports · 14% of its reports
Didn't stop worms after Ivermectin (Heartgard) 254 reports · 2.1% of its reports
Didn't stop worms after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 1,299 reports · 15% of its reports
Didn't stop worms after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 132 reports · 11% of its reports

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