Didn't stop ticks after Milbemycin Oxime (Interceptor) in dogs

The FDA has received 41 reports of didn't stop ticks in dogs after Milbemycin Oxime. That is 0.1% of all reports for this medicine, compared with 2.3% across reports for all dog medicines, so it is reported less often than average with this medicine.

41Reports

9.8%Marked serious

2.4%Recovered

2.4%Died or euthanised

45 daysTypical onset

How soon it started

Same day

1 4.5%

1–2 days

0 0.0%

3–7 days

1 4.5%

1–4 weeks

5 23%

Over a month

15 68%

How the animals did

Recovered

1 2.4%

Still unwell when reported

8 20%

Euthanised

1 2.4%

Not known

31 76%

Problems reported at the same time

Didn't work as expected

16 39%

3 7.3%

3 7.3%

2 4.9%

2 4.9%

2 4.9%

2 4.9%

2 4.9%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Milbemycin Oxime prevents heartworm and controls some intestinal worms (monthly).

Products with this ingredient include Interceptor. 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 Milbemycin Oxime cause didn't stop ticks in dogs?: 41 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 45 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 Selamectin (Revolution) 1,191 reports · 4.1% of its reports
Didn't stop ticks after Ivermectin (Heartgard) 38 reports · 0.3% of its reports

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