Weight gain after Milbemycin Oxime + Praziquantel (Interceptor Plus) in dogs

The FDA has received 575 reports of weight gain in dogs after Milbemycin Oxime + Praziquantel. That is 1.8% of all reports for this medicine, compared with 0.6% across reports for all dog medicines, so it is reported unusually often with this medicine.

575Reports

9.7%Marked serious

3.5%Recovered

1.4%Died or euthanised

155 daysTypical onset

How soon it started

Same day

23 9.1%

1–2 days

4 1.6%

3–7 days

5 2.0%

1–4 weeks

11 4.3%

Over a month

211 83%

How the animals did

Recovered

19 3.3%

Recovered with lasting effects

1 0.2%

Still unwell when reported

103 18%

Died

5 0.9%

Euthanised

3 0.5%

Not known

444 77%

Problems reported at the same time

Didn't prevent heartworm

339 59%

Didn't stop worms

70 12%

Weight loss

45 7.8%

Didn't work as expected

43 7.5%

37 6.4%

29 5.0%

22 3.8%

20 3.5%

Age of the animals

Under 1 year

1–3 years

282

4–7 years

172

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 weight gain in dogs?: 575 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 155 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).

Weight gain with similar medicines

Weight gain after Ivermectin + Pyrantel (Heartgard Plus) 596 reports · 0.4% of its reports
Weight gain after Milbemycin Oxime + Spinosad (Trifexis) 2,619 reports · 2.0% of its reports
Weight gain after Moxidectin (ProHeart 6) 93 reports · 0.2% of its reports
Weight gain after Milbemycin Oxime (Interceptor) 145 reports · 0.5% of its reports
Weight gain after Selamectin (Revolution) 47 reports · 0.2% of its reports
Weight gain after Ivermectin (Heartgard) 140 reports · 1.2% of its reports
Weight gain after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 23 reports · 0.3% of its reports
Weight gain after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 23 reports · 2.0% of its reports

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