Follow-Up: just started it. i am trying to get off a methampetamine addiction, but i nearly fall asleep all day for months after my attempts to quit. i cant get work done, and i am so lethargic, people actually comment. got the headaches someone mentioned, but they passed after a week. so far, this stuff has saved my life. i am funtional, but not speedy, but lost the "need" for the speediness. if i dont take it first thing in the morning, and wait ill late morning, it does affect my sleep the following nite. dont know anything about dose differences.