Interesting..Clonidine seems to be a very pharmacologically unique drug, and seeing I've never even taken a pharmacology class I couldn't really explain any more about it.
But yes, perhaps a downside or an upside to being human, the body is constantly pushed by our DNA's instructions to maintain an equilibrium throughout. And yes, with chronic opiate therapy, the receptors do become desensitized over time. Although there are new drugs coming out on the market that seem to specialize in regaining receptor sensitivity, such as Flumazenil for benzodiazepine withdrawal syndrome. Some of the opioid-antagonist/mixed-agonist/antagonist medication out now I believe provides a similar effect, no? Despite these drugs, a patients best route that is under opiate therapy, is to treat the symptoms physically rather than mentally, or with drugs. Pain can actually improve over time for many patients, depending on whatever the pain is deriving from of course.
Basically, as with many drugs of psychoactive use, chronically abusing them, like anything, will result in damagein some fashion. But, humans are as resilient as any other living thing on the planet, so if one is determined to recover fully, then they will..Never underestimate what the mind's effects have on the body.
Ibogaine being a perfect example.