never take someones pre - workout drink at the same dose, never. If he is using it, he has been for a while and has built a tolerance and is capable of handling the sides, you on the other hand can feel like your heart is going to explode.
it is such and individual thing, start small and add later if necessary, experiment conservatively.
A pro I know does this; 400 caffeine in an energy drink, 64mg of ephdrine, arginine, aspirin, tne, slin and gh.... all pre workout, that would give 99% of people a heart attack instantly.