I've never had to use it but here is the recommendation for a 50 pound dog:
*The protocol I follow is to use 3% Hydrogen Peroxide 2-3 teaspoons
every 10 min. repeat no more than 3 times. Do not do this if more
than 2 hours have passed since ingesting the object.
You don't want to induce vomiting if they have swallowed an acid or
solvent or , of course, sharp objects.*
Obviously, if you are sure that it went down and doesn't come back up with the help of the HP....off you go to the vet.
We had a scary "horka event" just last week. Our dogs have spoiled us and have never had "consumption" issues but when our 4 yo horka'd up a 4 inch long green thing I had no clue what it was...or could be. He had been just a bit "off" (more clingy/cuddly than usual) for a day but I didn't know why. When it came up, it was clear to me that it had been there for "a while". Once the "horkautopsy" was done it was determined to be carpet from a carpet square. I fell horrible that I had no idea what kind of help he needed and that it must have felt terrible to have that in his belly. I shudder to think of what he might have had to go through if it hadn't come up, with me swearing up and down that they "never' swallow anything they shouldn't.
I went out and bought a fresh bottle of HP just in case.
It's always helpful info to have tucked away in your brain...plus hydrogen peroxide is like 88 cents. Pretty cheap help if it's needed.