Low platelet count after Ivermectin (Heartgard) in dogs

The FDA has received 31 reports of low platelet count in dogs after Ivermectin. That is 0.3% of all reports for this medicine, compared with 0.2% across reports for all dog medicines.

31Reports
81%Marked serious
6.5%Recovered
42%Died or euthanised
31 daysTypical onset
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How soon it started

Same day
0 0.0%
1–2 days
4 20%
3–7 days
2 10%
1–4 weeks
4 20%
Over a month
10 50%

How the animals did

Recovered
1 3.2%
Recovered with lasting effects
1 3.2%
Still unwell when reported
11 35%
Died
7 23%
Euthanised
6 19%
Not known
5 16%

Problems reported at the same time

Age of the animals

Under 1 year
0
1–3 years
8
4–7 years
7
8–11 years
14
12+ years
2

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 low platelet count in dogs?
31 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 31 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).

Low platelet count with similar medicines

All reported side effects of Ivermectin in dogs · Medicines most reported with low platelet count