Urinary tract disorder after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 79 reports of urinary tract disorder in dogs after Milbemycin Oxime + Spinosad. That is 0.1% 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.

79Reports

38%Marked serious

34%Recovered

11%Died or euthanised

26 daysTypical onset

How soon it started

Same day

14 30%

1–2 days

3 6.4%

3–7 days

3 6.4%

1–4 weeks

4 8.5%

Over a month

23 49%

How the animals did

Recovered

19 24%

Recovered with lasting effects

8 10%

Still unwell when reported

19 24%

Died

2 2.5%

Euthanised

7 8.9%

Not known

24 30%

Problems reported at the same time

25 32%

17 22%

17 22%

14 18%

13 16%

10 13%

Didn't work as expected

9 11%

Urine abnormalities

9 11%

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 urinary tract disorder in dogs?: 79 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 26 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).

Urinary tract disorder with similar medicines

Urinary tract disorder after Ivermectin + Pyrantel (Heartgard Plus) 61 reports · 0.0% of its reports
Urinary tract disorder after Moxidectin (ProHeart 6) 32 reports · 0.1% of its reports
Urinary tract disorder after Milbemycin Oxime + Praziquantel (Interceptor Plus) 20 reports · 0.1% of its reports
Urinary tract disorder after Milbemycin Oxime (Interceptor) 41 reports · 0.1% of its reports
Urinary tract disorder after Selamectin (Revolution) 34 reports · 0.1% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with urinary tract disorder