it means it's the right kind. there's another called psr or something, and that's time-released, you don't want that.

i've had the same kind it's legit. it's one of the recommended ones to chug. (sippings better, have lots of water makes it a lot better, saltines if you've got nausea.)
TipTIP Reviewed by TipTIP on . DXM question (DXM HBr, USP?) I got Tussin Maximum Strength Cough, and the active ingredients list says "Dextromethorphan HBr, USP 15mg" What's the USP stand for? Is that something else? Rating: 5