Heart murmur after Milbemycin Oxime (Interceptor) in dogs

32 reports to the FDA describe heart murmur in dogs given Milbemycin Oxime. That is 0.1% of all reports for this medicine, compared with 0.2% across reports for all dog medicines, so it is reported less often than average with this medicine.

32Reports

75%Marked serious

16%Recovered

25%Died or euthanised

31 daysTypical onset

How soon it started

Same day

2 15%

1–2 days

1 7.7%

3–7 days

0 0.0%

1–4 weeks

3 23%

Over a month

7 54%

How the animals did

Recovered with lasting effects

5 16%

Still unwell when reported

10 31%

Died

4 13%

Euthanised

4 13%

Not known

9 28%

Problems reported at the same time

Vomiting

10 31%

Diarrhea

7 22%

Didn't prevent heartworm

7 22%

7 22%

6 19%

6 19%

6 19%

5 16%

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 heart murmur in dogs?: 32 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 31 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).

Heart murmur with similar medicines

Heart murmur after Ivermectin + Pyrantel (Heartgard Plus) 109 reports · 0.1% of its reports
Heart murmur after Milbemycin Oxime + Spinosad (Trifexis) 327 reports · 0.3% of its reports
Heart murmur after Moxidectin (ProHeart 6) 75 reports · 0.1% of its reports
Heart murmur after Milbemycin Oxime + Praziquantel (Interceptor Plus) 95 reports · 0.3% of its reports
Heart murmur after Ivermectin (Heartgard) 32 reports · 0.3% of its reports

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