Atropine is 1mL/20bs.
Epi is weight in lbs, divide by two, move the decimal point - or just weight in kgs, move decimal... but realistically, I don't do drug calculations for that. Just 0.05mL tiny dog/cat, 0.1mL small dog, 0.2mL slightly bigger dog, 0.3mL medium dog, 0.4mL lab, 0.5mL big big dog.
They're dead. ODing a titch ain't gonna make it worse.
Half the time they're rushed in and you don't have a real weight anyway, and getting your compressions going is more important anyway.
I'm five years out, almost a year into ER work and def don't have benadryl doses memorized...