About peroxide; Not the entire bottle at once! About a tablespoon, thrown to the back of the mouth/ throat for a big dog, and much less for smaller dogs, and can be repeated, maybe once, in 20 minutes or so.
Meanwhile, for really toxic stuff, load and go the the vet's, somewhere where they have injectable apomorphine, which will work every time.
When two of our three cats got into a house guest's meds here, neither cat responded to non- injectable apomorphine, and had to be in intensive care for several days, and both survived, only because of that care.
It's only money, right?!!
Try to give a pill to either cat, no way! Eat toxic drugs, why not?
Mary