Nystagmus after Milbemycin Oxime (Interceptor) in dogs

The FDA has received 42 reports of nystagmus in dogs after Milbemycin Oxime. That is 0.1% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported less often than average with this medicine.

42Reports

26%Marked serious

12%Recovered

14%Died or euthanised

124 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

1 10%

3–7 days

0 0.0%

1–4 weeks

2 20%

Over a month

7 70%

How the animals did

Recovered

3 7.1%

Recovered with lasting effects

2 4.8%

Still unwell when reported

6 14%

Died

5 12%

Euthanised

1 2.4%

Not known

25 60%

Problems reported at the same time

Wobbliness (ataxia)

22 52%

Seizures

12 29%

Vomiting

12 29%

Head tilt - ear disorder

10 24%

Vestibular disorder

10 24%

Tremors

9 21%

Recumbency

6 14%

Death

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).

Products with this ingredient include Interceptor. 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 cause nystagmus 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 124 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).

Nystagmus with similar medicines

Nystagmus after Ivermectin + Pyrantel (Heartgard Plus) 88 reports · 0.1% of its reports
Nystagmus after Milbemycin Oxime + Spinosad (Trifexis) 122 reports · 0.1% of its reports
Nystagmus after Moxidectin (ProHeart 6) 105 reports · 0.2% of its reports
Nystagmus after Milbemycin Oxime + Praziquantel (Interceptor Plus) 41 reports · 0.1% of its reports
Nystagmus after Selamectin (Revolution) 52 reports · 0.2% of its reports
Nystagmus after Ivermectin (Heartgard) 48 reports · 0.4% of its reports

All reported side effects of Milbemycin Oxime in dogs · Medicines most reported with nystagmus