I've tried potentiating my dillies with claratin, benadryl and Tagamet and have had zero luck. I've tried varying the injestion times and order and just got nothing. In fact I found that if I took benadryl before my opiates I didn't even feel the opiates!
A bit of dxm seemed to work, but since I don't use dxm very often it's hard to tell if it was a potentiated opiate high or just the dxm talking!
One thing I did try that made a difference was plugging the dilaudid pill itself (as in just shoving it up my butt as opposed to crushing it up into water first). I found it hit me harder AND lasted longer. When I plug the liquid, it takes 6-8 hours before withdrawls start to suck. When I plugged the pill itself, it takes 10-12 hours for wd to really kick in.
It's not potentiating per se but if you're reading this thread it means you're looking for a way to get more out of your opiates. The easiest way to do that is just try new routes of administration (ROA). If you've never snorted or plugged, try it.
If you've got the nerve to IV, obviously that awaits u as well.