Diarrhea after Ivermectin (Heartgard) in cats

51 reports to the FDA describe diarrhea in cats given Ivermectin. That is 5.3% of all reports for this medicine, compared with 5.1% across reports for all cat medicines.

51Reports
25%Marked serious
14%Recovered
12%Died or euthanised
1 daysTypical onset
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How soon it started

Same day
6 43%
1–2 days
4 29%
3–7 days
2 14%
1–4 weeks
0 0.0%
Over a month
2 14%

How the animals did

Recovered
7 14%
Still unwell when reported
1 2.0%
Died
6 12%
Not known
37 73%

Problems reported at the same time

23 45%
14 27%
5 9.8%
5 9.8%
Liver problems
4 7.8%

Age of the animals

Under 1 year
11
1–3 years
14
4–7 years
6
8–11 years
2
12+ years
7

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 diarrhea in cats?
51 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 1 day 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).

Diarrhea with similar medicines

All reported side effects of Ivermectin in cats · Medicines most reported with diarrhea