I'm not surprised that it didn't do too much to me. I'm REALLY hard to medicate. I'm one of those who wakes up on the operating table with GENERAL anesthesia. I've done it 3 times already. The doctors are amazed at my ability to take massive doses of medications. Of course they think I'm a junkie -- which I NEVER have been. I take after my Dad who would do the same thing. Don't have a clue what causes it, but it's a but unnerving when they're cutting on you and you can't tell them you're awake cause you're on your FACE while they're chopping up your spine!