Behaviour change after Milbemycin Oxime (Interceptor) in dogs

364 reports to the FDA describe behaviour change in dogs given Milbemycin Oxime. That is 1.2% of all reports for this medicine, compared with 2.5% across reports for all dog medicines, so it is reported less often than average with this medicine.

364Reports

26%Marked serious

24%Recovered

7.4%Died or euthanised

11 daysTypical onset

How soon it started

Same day

47 29%

1–2 days

17 11%

3–7 days

12 7.5%

1–4 weeks

11 6.9%

Over a month

73 46%

How the animals did

Recovered

77 21%

Recovered with lasting effects

11 3.0%

Still unwell when reported

68 19%

Died

20 5.5%

Euthanised

7 1.9%

Not known

181 50%

Problems reported at the same time

111 30%

73 20%

63 17%

52 14%

Restlessness or agitation

49 13%

Diarrhea

46 13%

Itching

34 9.3%

Seizures

33 9.1%

Age of the animals

Under 1 year

1–3 years

118

4–7 years

120

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 behaviour change in dogs?: 364 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 11 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).

Behaviour change with similar medicines

Behaviour change after Ivermectin + Pyrantel (Heartgard Plus) 1,674 reports · 1.1% of its reports
Behaviour change after Milbemycin Oxime + Spinosad (Trifexis) 4,099 reports · 3.2% of its reports
Behaviour change after Moxidectin (ProHeart 6) 688 reports · 1.4% of its reports
Behaviour change after Milbemycin Oxime + Praziquantel (Interceptor Plus) 852 reports · 2.7% of its reports
Behaviour change after Selamectin (Revolution) 652 reports · 2.2% of its reports
Behaviour change after Ivermectin (Heartgard) 368 reports · 3.1% of its reports
Behaviour change after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 146 reports · 1.7% of its reports
Behaviour change after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 55 reports · 4.7% of its reports

All reported side effects of Milbemycin Oxime in dogs · Medicines most reported with behaviour change