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

The FDA has received 118 reports of didn't stop fleas in dogs after Milbemycin Oxime. That is 0.4% of all reports for this medicine, compared with 6.2% across reports for all dog medicines, so it is reported less often than average with this medicine.

118Reports

11%Marked serious

20%Recovered

0.8%Died or euthanised

92 daysTypical onset

How soon it started

Same day

6 9.0%

1–2 days

3 4.5%

3–7 days

2 3.0%

1–4 weeks

13 19%

Over a month

43 64%

How the animals did

Recovered

10 8.5%

Recovered with lasting effects

14 12%

Still unwell when reported

16 14%

Died

1 0.8%

Not known

77 65%

Problems reported at the same time

Itching

25 21%

Vomiting

11 9.3%

Overdose

8 6.8%

Didn't work as expected

6 5.1%

Behaviour change

6 5.1%

Lethargy

5 4.2%

Unpalatable

5 4.2%

Restlessness or agitation

5 4.2%

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 fleas in dogs?: 118 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 92 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 fleas with similar medicines

Didn't stop fleas after Ivermectin + Pyrantel (Heartgard Plus) 483 reports · 0.3% of its reports
Didn't stop fleas after Milbemycin Oxime + Spinosad (Trifexis) 8,717 reports · 6.7% of its reports
Didn't stop fleas after Moxidectin (ProHeart 6) 70 reports · 0.1% of its reports
Didn't stop fleas after Milbemycin Oxime + Praziquantel (Interceptor Plus) 171 reports · 0.5% of its reports
Didn't stop fleas after Selamectin (Revolution) 3,379 reports · 11% of its reports
Didn't stop fleas after Ivermectin (Heartgard) 451 reports · 3.8% of its reports
Didn't stop fleas after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 38 reports · 0.4% of its reports
Didn't stop fleas after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 21 reports · 1.8% of its reports

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