25-50mg of ephedrine is what I used to take. I am sure 120mg would give most people a heart attack, or at least make them feel like they are having one.
I would not do more than 25mg in a single dose and that is still pretty high.
The only thing I disliked about Ephedrine is it made my dick kinda shrivel when I was not erect. Just a weird kinda not hanging out situation. But when it got up it was cool, normal size.
Some guys here mentioned Clen, I would stay the fuck away from Clenbuterol.
Here is a great podcast about Clenbuterol and how to use it but why you should probably not use it: