It kinda works differently for rodents.
It's all in the dosage.
I am on Warfarin for life due to Factor 5 Leiden. Keeps my blood from clotting and almost killing me 3 times already.
Basically, it kills rodents due to the dosage. They get a massive dose, which then kills them. Humans get a therapeutic dose that keeps your blood “thinned” to a specific point.
They keep trying to get me on one of the new wonder drugs to replace Warfarin, but they seem to have some significant side effects so I'll just stick with what seems to work.