Constipation after Milbemycin Oxime + Praziquantel (Interceptor Plus) in dogs

The FDA has received 42 reports of constipation in dogs after Milbemycin Oxime + Praziquantel. That is 0.1% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

42Reports

29%Marked serious

17%Recovered

7.1%Died or euthanised

45 daysTypical onset

How soon it started

Same day

2 9.1%

1–2 days

1 4.5%

3–7 days

3 14%

1–4 weeks

3 14%

Over a month

13 59%

How the animals did

Recovered

7 17%

Still unwell when reported

14 33%

Died

3 7.1%

Not known

18 43%

Problems reported at the same time

20 48%

18 43%

14 33%

12 29%

10 24%

8 19%

Didn't work as expected

8 19%

Dehydration

6 14%

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). 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 constipation in dogs?: 42 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 45 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).

Constipation with similar medicines

Constipation after Ivermectin + Pyrantel (Heartgard Plus) 105 reports · 0.1% of its reports
Constipation after Milbemycin Oxime + Spinosad (Trifexis) 152 reports · 0.1% of its reports
Constipation after Moxidectin (ProHeart 6) 33 reports · 0.1% of its reports
Constipation after Milbemycin Oxime (Interceptor) 24 reports · 0.1% of its reports
Constipation after Selamectin (Revolution) 33 reports · 0.1% of its reports

All reported side effects of Milbemycin Oxime + Praziquantel in dogs · Medicines most reported with constipation