The key might be in the bipolar issues. I am schizophrenic, and while opioids work just fine on me, anesthetics do not. I require heroic doses for even a moderate local result, which then does not last nearly long enough for say, a regular root canal. My dentist was at first very skeptical, but when I jumped two feet out of his chair he acquiesced and gave me another shot, then a third (additional to the first few), and even then I was coming 'round as he was just finishng.
He prescribed me percs, and I almost laughed as he warned me of their "vicious strength and debilitating effects".
I took them all (10) that night after a quick CW extraction.