Blood problems after Ivermectin (Heartgard) in dogs

The FDA has received 145 reports of blood problems in dogs after Ivermectin. That is 1.2% of all reports for this medicine, compared with 1.8% across reports for all dog medicines.

145Reports

70%Marked serious

12%Recovered

30%Died or euthanised

54 daysTypical onset

How soon it started

Same day

8 9.8%

1–2 days

3 3.7%

3–7 days

5 6.1%

1–4 weeks

15 18%

Over a month

51 62%

How the animals did

Recovered

12 8.3%

Recovered with lasting effects

6 4.1%

Still unwell when reported

55 38%

Died

15 10%

Euthanised

28 19%

Not known

29 20%

Problems reported at the same time

74 51%

60 41%

45 31%

44 30%

42 29%

34 23%

30 21%

28 19%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

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 blood problems in dogs?: 145 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 54 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).

Blood problems with similar medicines

Blood problems after Ivermectin + Pyrantel (Heartgard Plus) 545 reports · 0.4% of its reports
Blood problems after Milbemycin Oxime + Spinosad (Trifexis) 735 reports · 0.6% of its reports
Blood problems after Moxidectin (ProHeart 6) 1,343 reports · 2.7% of its reports
Blood problems after Milbemycin Oxime + Praziquantel (Interceptor Plus) 225 reports · 0.7% of its reports
Blood problems after Milbemycin Oxime (Interceptor) 251 reports · 0.8% of its reports
Blood problems after Selamectin (Revolution) 327 reports · 1.1% of its reports
Blood problems after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 37 reports · 0.4% of its reports
Blood problems after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 30 reports · 2.6% of its reports

All reported side effects of Ivermectin in dogs · Medicines most reported with blood problems