alkaloids + empty stomach = BARF!!!!!!
My training partner found that out the hard way yesterday.
You're best bet is to take with something small 45 minutes prior, if you want to take it. Ephedrine is going to increase your heartrate, so you're not gonna have as much 'wind' if this is the route you're thinking of taking. The benefits come from the increase in epinephrine and norepinephrine to give you mental focus.