I have the same issue. I was prescribed percocet years ago for an broken bone and arthritis.. So as expected my tolerance rose. I can now take 3 or 4 oxy 30's, valium, alazporam, dilaudid and a popular herbal remedy.. LITERALLY one right after the other..and STILL not get much notable effect

Even if I go thru the hell of detox, it still doesn't seem to change my tolerance. I've done grapefruit juice, cimetadine, avacado, heck pretty much everything to old wives tales but NOTHING works. I have to draw (my personal) line b4 heroin... So I'm hoping ANYONE can give some insight into something that actually works! I was even exploring the affect long term use has affected my dopamine production, etc... I'm even trying herbal DHA. Any suggestions for a true potentiator?? I'm not superhuman, so it's definitely become a major source of irritation that I can get no relief
I don't suggest you or anyone else take anything I'm about to say as a recommendation, but I'm going to attempt to relay some scientific information about things you're wondering about.
First of all, I'm curious as to what the popular herbal remedy is you referred to. Is it perhaps kava? If so, I have yet to find a store bought supplement form of kava that produces any noticeable effects, be it capsules, liquid in a dropper bottle, or tea bags. All the ones I've tried are extracts, some containing what should be relatively high doses in the form of kavalactones. The only one that even produced the signature numbing effect was a certain liquid extract in a dropper bottle, but still there were no discernible psychoactive effects. Anyway, I have cold-brewed kava tea with milk in the past using fresh root powder and felt definite psychoactivity. I can't recall if I combined it with opioids ever, but I would venture to guess that the mellow, relaxed state the kava produced would synergize very nicely with them when used responsibly.
As for potentiators, I have lots of experience with the ones mentioned and others taken prior to opioid administration with perceived effect. However, they only potentiate opioids taken orally and even then the potentiation is not as pronounced as many people would like to believe it's going to be. Ime the peak plasma level of the opioid doesn't seem to increase as much as the duration of the experience seems to. I used to have an almost ritualistic regimen of drugs I would take around an hour prior to orally ingesting any opioids. Also, one has to remember that you don't want to attempt potentiation with prodrugs such as codeine because then they will limit the amount of active drug produced instead.
I used to use opioids on a daily basis and believe that messed with my dopamine and/or other neurotransmitters as well, be it directly or indirectly. Phenibut use seems to have brought the levels of those neurotransmitters back up to where they were prior to opioid and other drug use (drugs such as benzodiazepines, alcohol, and psychostimulants; drugs I believe also at least played a part in this possible neurotransmitter deficiency). Even after abstaining from phenibut this effect persisted and I felt more motivation, ambition, a lot less apathy, and an overall increase in mood.
I'll be receiving some tianeptine in the mail tomorrow which I know isn't a great example for studying typical opioid tolerance, but I've been taking a form of chelated magnesium along with some other supplements and will also be taking most or all of the potentiators I used to ingest prior to my opioid experiences. I'll post a general review of how it goes with said tianeptine in this thread within the next few days. I took tianeptine for two to three days in a row around a few weeks ago, but am hoping I didn't retain much, if any, tolerance from that bout. Prior to that, I hadn't used any opioid for months and even then it was here and there once in a long while and for one or two days, three consecutive days tops as I haven't used on a regular basis in almost two years.
Alright, time for me to get some sleep since I've been making use of phenibut's ability to cause me to feel well rested after only a few hours or so of sleep lately. Just figured I'd add my thoughts about all this.