Underdose after Milbemycin Oxime (Interceptor) in dogs

The FDA has received 118 reports of underdose in dogs after Milbemycin Oxime. That is 0.4% of all reports for this medicine, compared with 1.0% across reports for all dog medicines, so it is reported less often than average with this medicine.

118Reports

41%Marked serious

16%Recovered

2.5%Died or euthanised

107 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

4 13%

3–7 days

1 3.2%

1–4 weeks

6 19%

Over a month

20 65%

How the animals did

Recovered

17 14%

Recovered with lasting effects

2 1.7%

Still unwell when reported

42 36%

Died

2 1.7%

Euthanised

1 0.8%

Not known

54 46%

Problems reported at the same time

Didn't prevent heartworm

56 47%

Didn't stop worms

21 18%

Didn't work as expected

21 18%

19 16%

8 6.8%

7 5.9%

6 5.1%

6 5.1%

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 underdose 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 107 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).

Underdose with similar medicines

Underdose after Ivermectin + Pyrantel (Heartgard Plus) 1,810 reports · 1.2% of its reports
Underdose after Milbemycin Oxime + Spinosad (Trifexis) 750 reports · 0.6% of its reports
Underdose after Moxidectin (ProHeart 6) 180 reports · 0.4% of its reports
Underdose after Milbemycin Oxime + Praziquantel (Interceptor Plus) 153 reports · 0.5% of its reports
Underdose after Selamectin (Revolution) 179 reports · 0.6% of its reports
Underdose after Ivermectin (Heartgard) 99 reports · 0.8% of its reports
Underdose after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 98 reports · 1.1% of its reports

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