I still seem to be having side effects that didn't seem to kick in until being on this drug for about two weeks. I get horrible headaches, racing heart rates, an occasional anxiety attacks. My doctor tells me to hang in there, that these will subside in time... however... I'm miserable. Arguably though I don't have any back pain. So it's doing the job that way..but how long will these side effects continue? I'd rather hear from patients that have actually experienced these side effects and how long they lasted. And yes, I did the whole Vicodin, Oxy, Fentanyl routine and just didn't want to feel like I was just "existing". My doc says his patients have had phenomenal success with this drug however, I'm becoming doubtful. Any and all replies will be greatly appreciated. Thanks for listening.