[My Beau]

Nope, like Appyt said most dewormers are safe in way higher doses than normally given.

Ivermectin, up to 60x the reccommended amount; fenbendazole, 100-200x; pyrantel pamoate, 20x. The one you have to watch is moxidectin, 5x a normal dose can do serious damage, but even if your horse was dewormed with this 2x, I wouldn't worry, considering he's probably very healthy.

 

[My Beau]

Not saying it should be, but it certainly won't harm a horse at 2x the recommended dose when it's been safely tested to 60x.

 

[My Beau]

He should be just fine. I actually use a double ivermectin in my deworming program - vet didn't have a problem with it.