Didn't work as expected after Ivermectin + Praziquantel in horses

The FDA has received 86 reports of didn't work as expected in horses after Ivermectin + Praziquantel. That is 3.2% of all reports for this medicine, compared with 23% across reports for all horse medicines, so it is reported less often than average with this medicine.

86Reports
15%Marked serious
0.0%Recovered
13%Died or euthanised
30 daysTypical onset
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How soon it started

Same day
2 17%
1–2 days
0 0.0%
3–7 days
1 8.3%
1–4 weeks
5 42%
Over a month
4 33%

How the animals did

Still unwell when reported
3 3.5%
Died
9 10%
Euthanised
2 2.3%
Not known
72 84%

Problems reported at the same time

Digestive tract disorder
14 16%
Didn't stop worms
12 14%
Death
11 13%
Weight loss
9 10%
Abdominal pain
7 8.1%
Overdose
6 7.0%
Loss of condition
5 5.8%
Diarrhea
4 4.7%

Age of the animals

Under 1 year
16
1–3 years
14
4–7 years
11
8–11 years
7
12+ years
10

About this medicine

Ivermectin prevents heartworm disease (monthly). Praziquantel treats tapeworms.

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 + Praziquantel cause didn't work as expected in horses?
86 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 30 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).

Didn't work as expected with similar medicines

All reported side effects of Ivermectin + Praziquantel in horses · Medicines most reported with didn't work as expected