Inappropriate urination after Milbemycin Oxime + Spinosad (Trifexis) in dogs

The FDA has received 494 reports of inappropriate urination in dogs after Milbemycin Oxime + Spinosad. That is 0.4% of all reports for this medicine, compared with 0.5% across reports for all dog medicines.

494Reports

49%Marked serious

54%Recovered

10%Died or euthanised

1 daysTypical onset

How soon it started

Same day

157 40%

1–2 days

54 14%

3–7 days

17 4.3%

1–4 weeks

25 6.4%

Over a month

139 35%

How the animals did

Recovered

181 37%

Recovered with lasting effects

84 17%

Still unwell when reported

75 15%

Died

29 5.9%

Euthanised

21 4.3%

Not known

104 21%

Problems reported at the same time

219 44%

184 37%

131 27%

117 24%

91 18%

78 16%

70 14%

67 14%

Age of the animals

Under 1 year

101

1–3 years

145

4–7 years

122

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 inappropriate urination in dogs?: 494 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 1 day 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).

Inappropriate urination with similar medicines

Inappropriate urination after Ivermectin + Pyrantel (Heartgard Plus) 352 reports · 0.2% of its reports
Inappropriate urination after Moxidectin (ProHeart 6) 168 reports · 0.3% of its reports
Inappropriate urination after Milbemycin Oxime + Praziquantel (Interceptor Plus) 124 reports · 0.4% of its reports
Inappropriate urination after Milbemycin Oxime (Interceptor) 34 reports · 0.1% of its reports
Inappropriate urination after Selamectin (Revolution) 35 reports · 0.1% of its reports
Inappropriate urination after Ivermectin (Heartgard) 60 reports · 0.5% of its reports
Inappropriate urination after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 20 reports · 0.2% of its reports

All reported side effects of Milbemycin Oxime + Spinosad in dogs · Medicines most reported with inappropriate urination