Underdose after Ivermectin (Heartgard) in dogs

99 reports to the FDA describe underdose in dogs given Ivermectin. That is 0.8% of all reports for this medicine, compared with 1.0% across reports for all dog medicines.

99Reports

33%Marked serious

15%Recovered

2.0%Died or euthanised

33 daysTypical onset

How soon it started

Same day

4 12%

1–2 days

2 6.1%

3–7 days

3 9.1%

1–4 weeks

3 9.1%

Over a month

21 64%

How the animals did

Recovered

11 11%

Recovered with lasting effects

4 4.0%

Still unwell when reported

32 32%

Euthanised

2 2.0%

Not known

50 51%

Problems reported at the same time

Didn't prevent heartworm

46 46%

Didn't work as expected

14 14%

13 13%

13 13%

12 12%

11 11%

5 5.1%

5 5.1%

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 underdose in dogs?: 99 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 33 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).

Underdose with similar medicines

Underdose after Ivermectin + Pyrantel (Heartgard Plus) 1,810 reports · 1.2% of its reports
Underdose after Milbemycin Oxime + Spinosad (Trifexis) 750 reports · 0.6% of its reports
Underdose after Moxidectin (ProHeart 6) 180 reports · 0.4% of its reports
Underdose after Milbemycin Oxime + Praziquantel (Interceptor Plus) 153 reports · 0.5% of its reports
Underdose after Milbemycin Oxime (Interceptor) 118 reports · 0.4% of its reports
Underdose after Selamectin (Revolution) 179 reports · 0.6% of its reports
Underdose after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 98 reports · 1.1% of its reports

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