What type of dog?
What type of heartworm pill?
Thank you for the extra information.
There are some breeds that are sensitive to the ivermectin in Heartgard but the Elo dog is not one of those breeds.
Ivermectin which is the active ingredient in heartgard has a very wide margin of safety. I am assuming she ate 11 of the 51-100 pound heartgard. That size heartgard contains 272 mcg of ivermectin.
The dose at which we see clinical signs in dogs can be seen at as little as 1000 mcg/kg in a single dose.
So let's do the math:
Your dog received 2992 mcg of Ivermectin
Her toxic dose would be around 25000 mcg.
By the numbers, her dose is no where close to dangerous but we know some dogs can be sensitive. Even at the dose that causes problems in those breeds, she would still be way underneath a toxic dose. Signs to watch for would be dilation of the eyes or tremors but I don't think you should have any problems!
I hope that helps!