Tchort what are your thoughts on doxylamine? I always felt it was a much cleaner feeling and added more euphoria when combined with opiates than any other I've tried. I feel the same way about hydrozyxzine as well... I felt the 2 aforementioned were far more anxiolytic and euphoric than others I have tried... promethazine, diphenhydramine, dimenhydrinate, and if you want to include drugs with strong antihistaminergic side effects like cyclobenzaprine, quetiapine, trazodone, etc.
I've always been interested in combining orphenadrine with opiates for pain relief/muscle relaxation and to see if it was more euphoric than doxylamine or hydroxyzine were for me.