Decreased percentage of reticulocytes after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 34 reports of decreased percentage of reticulocytes in dogs after Ivermectin + Pyrantel. That is 0.0% of all reports for this medicine, compared with 0.0% across reports for all dog medicines, so it is reported less often than average with this medicine.

34Reports
50%Marked serious
8.8%Recovered
15%Died or euthanised
18 daysTypical onset
SponsoredWorried about your pet? Ask a veterinarian online, 24/7

How soon it started

Same day
2 7.7%
1–2 days
6 23%
3–7 days
3 12%
1–4 weeks
5 19%
Over a month
10 38%

How the animals did

Recovered
3 8.8%
Still unwell when reported
10 29%
Died
2 5.9%
Euthanised
3 8.8%
Not known
16 47%

Problems reported at the same time

Age of the animals

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

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 decreased percentage of reticulocytes in dogs?
34 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 18 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).

Decreased percentage of reticulocytes with similar medicines

All reported side effects of Ivermectin + Pyrantel in dogs · Medicines most reported with decreased percentage of reticulocytes