Didn't work as expected after Milbemycin Oxime + Praziquantel (Interceptor Plus) in dogs

The FDA has received 3,979 reports of didn't work as expected in dogs after Milbemycin Oxime + Praziquantel. That is 13% of all reports for this medicine, compared with 13% across reports for all dog medicines.

3,979Reports

6.0%Marked serious

1.8%Recovered

0.6%Died or euthanised

130 daysTypical onset

How soon it started

Same day

27 2.5%

1–2 days

19 1.8%

3–7 days

36 3.4%

1–4 weeks

137 13%

Over a month

847 79%

How the animals did

Recovered

62 1.6%

Recovered with lasting effects

10 0.3%

Still unwell when reported

335 8.4%

Died

13 0.3%

Euthanised

10 0.3%

Not known

3,549 89%

Problems reported at the same time

528 13%

182 4.6%

160 4.0%

146 3.7%

98 2.5%

84 2.1%

Didn't prevent heartworm

71 1.8%

Lameness

49 1.2%

Age of the animals

Under 1 year

652

1–3 years

1,568

4–7 years

906

8–11 years

559

12+ years

212

About this medicine

Milbemycin Oxime prevents heartworm and controls some intestinal worms (monthly). Praziquantel treats tapeworms.

Products with this combination include Interceptor Plus. 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 + Praziquantel cause didn't work as expected in dogs?: 3,979 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 130 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).

Didn't work as expected with similar medicines

Didn't work as expected after Ivermectin + Pyrantel (Heartgard Plus) 27,781 reports · 19% of its reports
Didn't work as expected after Milbemycin Oxime + Spinosad (Trifexis) 13,050 reports · 10% of its reports
Didn't work as expected after Moxidectin (ProHeart 6) 2,005 reports · 4.0% of its reports
Didn't work as expected after Milbemycin Oxime (Interceptor) 3,131 reports · 11% of its reports
Didn't work as expected after Selamectin (Revolution) 2,253 reports · 7.7% of its reports
Didn't work as expected after Ivermectin (Heartgard) 741 reports · 6.2% of its reports
Didn't work as expected after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 1,337 reports · 16% of its reports
Didn't work as expected after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 123 reports · 11% of its reports

All reported side effects of Milbemycin Oxime + Praziquantel in dogs · Medicines most reported with didn't work as expected