I have literatly had only one dose I was prescribed it yesterday and took my first dose last night (8:30 pm). At first I felt this over-whelming feeling of exhaustion to the point of I couldn't even get up on my own. As it came time to lay down I just could not sleep, and I have yet to sleep, it is well over 12 hours since my first dose, and im not sure if I should take another one. I am prescribed one every 8 hours.