Heart murmur after Milbemycin Oxime + Spinosad (Trifexis) in dogs

327 reports to the FDA describe heart murmur in dogs given Milbemycin Oxime + Spinosad. That is 0.3% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

327Reports

78%Marked serious

29%Recovered

18%Died or euthanised

61 daysTypical onset

How soon it started

Same day

31 21%

1–2 days

13 8.7%

3–7 days

9 6.0%

1–4 weeks

12 8.0%

Over a month

85 57%

How the animals did

Recovered

14 4.3%

Recovered with lasting effects

81 25%

Still unwell when reported

100 31%

Died

34 10%

Euthanised

25 7.6%

Not known

73 22%

Problems reported at the same time

87 27%

79 24%

65 20%

57 17%

Didn't prevent heartworm

50 15%

Breathing problems

48 15%

Liver problems

47 14%

Diarrhea

44 13%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

133

12+ years

About this medicine

Milbemycin Oxime prevents heartworm and controls some intestinal worms (monthly). Spinosad kills fleas; monthly chewable.

Products with this combination include Trifexis. 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 + Spinosad cause heart murmur 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 61 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 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 Milbemycin Oxime (Interceptor) 32 reports · 0.1% of its reports
Heart murmur after Ivermectin (Heartgard) 32 reports · 0.3% of its reports

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