Decreased packed cell volume (pcv) after Milbemycin Oxime + Spinosad (Trifexis) in dogs

40 reports to the FDA describe decreased packed cell volume (pcv) in dogs given Milbemycin Oxime + Spinosad. That is 0.0% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported less often than average with this medicine.

40Reports

93%Marked serious

20%Recovered

33%Died or euthanised

2 daysTypical onset

How soon it started

Same day

8 35%

1–2 days

4 17%

3–7 days

0 0.0%

1–4 weeks

4 17%

Over a month

7 30%

How the animals did

Recovered

6 15%

Recovered with lasting effects

2 5.0%

Still unwell when reported

13 33%

Died

4 10%

Euthanised

9 23%

Not known

6 15%

Problems reported at the same time

24 60%

23 57%

20 50%

19 48%

15 38%

14 35%

13 33%

13 33%

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). 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 decreased packed cell volume (pcv) in dogs?: 40 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 2 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).

Decreased packed cell volume (pcv) with similar medicines

Decreased packed cell volume (pcv) after Ivermectin + Pyrantel (Heartgard Plus) 100 reports · 0.1% of its reports
Decreased packed cell volume (pcv) after Moxidectin (ProHeart 6) 76 reports · 0.2% of its reports
Decreased packed cell volume (pcv) after Milbemycin Oxime + Praziquantel (Interceptor Plus) 25 reports · 0.1% of its reports
Decreased packed cell volume (pcv) after Ivermectin (Heartgard) 24 reports · 0.2% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with decreased packed cell volume (pcv)