Low platelet count after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 137 reports of low platelet count in dogs after Ivermectin + Pyrantel. That is 0.1% of all reports for this medicine, compared with 0.2% across reports for all dog medicines, so it is reported less often than average with this medicine.

137Reports
70%Marked serious
19%Recovered
15%Died or euthanised
9 daysTypical onset
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How soon it started

Same day
14 18%
1–2 days
16 21%
3–7 days
7 9.2%
1–4 weeks
15 20%
Over a month
24 32%

How the animals did

Recovered
17 12%
Recovered with lasting effects
9 6.6%
Still unwell when reported
44 32%
Died
5 3.6%
Euthanised
15 11%
Not known
47 34%

Problems reported at the same time

Age of the animals

Under 1 year
10
1–3 years
40
4–7 years
41
8–11 years
35
12+ years
9

About this medicine

Ivermectin prevents heartworm disease (monthly). Pyrantel treats roundworms and hookworms.

Products with this combination include Heartgard Plus, Tri-Heart Plus, Iverhart 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 Ivermectin + Pyrantel cause low platelet count in dogs?
137 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 9 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 + Pyrantel in dogs · Medicines most reported with low platelet count