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

The FDA has received 1,191 reports of didn't stop ticks in dogs after Selamectin. That is 4.1% of all reports for this medicine, compared with 2.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

1,191Reports

4.3%Marked serious

1.8%Recovered

1.3%Died or euthanised

40 daysTypical onset

How soon it started

Same day

23 13%

1–2 days

8 4.7%

3–7 days

19 11%

1–4 weeks

24 14%

Over a month

97 57%

How the animals did

Recovered

21 1.8%

Still unwell when reported

145 12%

Died

10 0.8%

Euthanised

6 0.5%

Not known

1,009 85%

Problems reported at the same time

Didn't stop fleas

234 20%

Didn't work as expected

75 6.3%

37 3.1%

36 3.0%

35 2.9%

33 2.8%

Didn't prevent heartworm

32 2.7%

Vomiting

31 2.6%

Age of the animals

Under 1 year

131

1–3 years

347

4–7 years

224

8–11 years

134

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 ticks in dogs?: 1,191 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 40 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 ticks with similar medicines

Didn't stop ticks after Ivermectin + Pyrantel (Heartgard Plus) 438 reports · 0.3% of its reports
Didn't stop ticks after Milbemycin Oxime + Spinosad (Trifexis) 312 reports · 0.2% of its reports
Didn't stop ticks after Milbemycin Oxime + Praziquantel (Interceptor Plus) 311 reports · 1.0% of its reports
Didn't stop ticks after Milbemycin Oxime (Interceptor) 41 reports · 0.1% of its reports
Didn't stop ticks after Ivermectin (Heartgard) 38 reports · 0.3% of its reports

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