Ironic this subject would come up here, at this time.
Talked to a close friend today, who has been paralyzed, for around 10 years. His spine was broken in 2 places, when he was throw from his bicycle.
He takes lots of opiates, as around 30% of spinal injuries have sensations, similar to "phantom limb", as amputees do. Long story short, medical research is now showing that opiates not only act on the pain receptors, in the brain, but they also inflame the nerve endings.
End result in his case he is now going through a phase where the opiates are wearing off more quickly than they have, and when they do, he is in greater pain than he was before taking them. The nerve inflammation they are creating is making his situation worse.
He has switched to an unconventional pain management regimen, that avoids the nerve inflammation problem. It is obviously non-opiate based. The initial results are promising.