Abnormal pupil light reflex after Ivermectin (Heartgard) in dogs

The FDA has received 54 reports of abnormal pupil light reflex in dogs after Ivermectin. That is 0.4% of all reports for this medicine, compared with 0.1% across reports for all dog medicines, so it is reported unusually often with this medicine.

54Reports
81%Marked serious
57%Recovered
7.4%Died or euthanised
38 daysTypical onset
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How soon it started

Same day
6 15%
1–2 days
3 7.5%
3–7 days
1 2.5%
1–4 weeks
7 18%
Over a month
23 57%

How the animals did

Recovered
23 43%
Recovered with lasting effects
8 15%
Still unwell when reported
3 5.6%
Euthanised
4 7.4%
Not known
16 30%

Problems reported at the same time

Eye or vision problems
40 74%
Wobbliness (ataxia)
22 41%
Abnormal menace reflex test
19 35%
Tremors
19 35%
Labelled drug-drug interaction medication error
16 30%
Vomiting
11 20%
Lethargy
11 20%
Dilated pupils
10 19%

Age of the animals

Under 1 year
21
1–3 years
14
4–7 years
6
8–11 years
5
12+ years
4

About this medicine

Ivermectin prevents heartworm disease (monthly).

Products with this ingredient include Heartgard. 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 Ivermectin cause abnormal pupil light reflex in dogs?
54 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 38 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).

Abnormal pupil light reflex with similar medicines

All reported side effects of Ivermectin in dogs · Medicines most reported with abnormal pupil light reflex