Weakness after Milbemycin Oxime (Interceptor) in dogs

223 reports to the FDA describe weakness in dogs given Milbemycin Oxime. That is 0.7% of all reports for this medicine, compared with 1.4% across reports for all dog medicines, so it is reported less often than average with this medicine.

223Reports

26%Marked serious

13%Recovered

21%Died or euthanised

3 daysTypical onset

How soon it started

Same day

16 26%

1–2 days

15 24%

3–7 days

4 6.5%

1–4 weeks

7 11%

Over a month

20 32%

How the animals did

Recovered

29 13%

Recovered with lasting effects

1 0.4%

Still unwell when reported

31 14%

Died

38 17%

Euthanised

8 3.6%

Not known

116 52%

Problems reported at the same time

98 44%

76 34%

70 31%

54 24%

47 21%

45 20%

34 15%

32 14%

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 weakness in dogs?: 223 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 3 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).

Weakness with similar medicines

Weakness after Ivermectin + Pyrantel (Heartgard Plus) 453 reports · 0.3% of its reports
Weakness after Milbemycin Oxime + Spinosad (Trifexis) 847 reports · 0.7% of its reports
Weakness after Moxidectin (ProHeart 6) 913 reports · 1.8% of its reports
Weakness after Milbemycin Oxime + Praziquantel (Interceptor Plus) 256 reports · 0.8% of its reports
Weakness after Selamectin (Revolution) 214 reports · 0.7% of its reports
Weakness after Ivermectin (Heartgard) 229 reports · 1.9% of its reports
Weakness after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 76 reports · 0.9% of its reports

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