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

The FDA has received 76 reports of monocytosis in dogs after Milbemycin Oxime + Praziquantel. That is 0.2% of all reports for this medicine, compared with 0.3% across reports for all dog medicines.

76Reports

76%Marked serious

14%Recovered

21%Died or euthanised

28 daysTypical onset

How soon it started

Same day

2 4.3%

1–2 days

8 17%

3–7 days

5 11%

1–4 weeks

9 19%

Over a month

23 49%

How the animals did

Recovered

9 12%

Recovered with lasting effects

2 2.6%

Still unwell when reported

24 32%

Died

6 7.9%

Euthanised

10 13%

Not known

25 33%

Problems reported at the same time

35 46%

35 46%

34 45%

34 45%

28 37%

26 34%

22 29%

18 24%

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 monocytosis in dogs?: 76 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 28 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).

Monocytosis with similar medicines

Monocytosis after Ivermectin + Pyrantel (Heartgard Plus) 185 reports · 0.1% of its reports
Monocytosis after Milbemycin Oxime + Spinosad (Trifexis) 96 reports · 0.1% of its reports
Monocytosis after Moxidectin (ProHeart 6) 177 reports · 0.3% of its reports
Monocytosis after Milbemycin Oxime (Interceptor) 29 reports · 0.1% of its reports
Monocytosis after Selamectin (Revolution) 36 reports · 0.1% of its reports
Monocytosis after Ivermectin (Heartgard) 31 reports · 0.3% of its reports

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