Loose stool after Milbemycin Oxime (Interceptor) in dogs

The FDA has received 327 reports of loose stool in dogs after Milbemycin Oxime. That is 1.1% of all reports for this medicine, compared with 0.9% across reports for all dog medicines.

327Reports

8.6%Marked serious

8.9%Recovered

2.4%Died or euthanised

11 daysTypical onset

How soon it started

Same day

12 24%

1–2 days

6 12%

3–7 days

4 7.8%

1–4 weeks

11 22%

Over a month

18 35%

How the animals did

Recovered

28 8.6%

Recovered with lasting effects

1 0.3%

Still unwell when reported

33 10%

Died

6 1.8%

Euthanised

2 0.6%

Not known

257 79%

Problems reported at the same time

Didn't stop worms

109 33%

Vomiting

73 22%

Didn't work as expected

61 19%

60 18%

57 17%

28 8.6%

14 4.3%

Digestive tract disorder

13 4.0%

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 loose stool in dogs?: 327 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).

Loose stool with similar medicines

Loose stool after Ivermectin + Pyrantel (Heartgard Plus) 1,339 reports · 0.9% of its reports
Loose stool after Milbemycin Oxime + Spinosad (Trifexis) 885 reports · 0.7% of its reports
Loose stool after Moxidectin (ProHeart 6) 332 reports · 0.7% of its reports
Loose stool after Milbemycin Oxime + Praziquantel (Interceptor Plus) 406 reports · 1.3% of its reports
Loose stool after Selamectin (Revolution) 156 reports · 0.5% of its reports
Loose stool after Ivermectin (Heartgard) 88 reports · 0.7% of its reports
Loose stool after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 120 reports · 1.4% of its reports

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