Morphine addiction is the model upon which the current perception of addiction is based.Animal and human studies and clinical experience back up the contention that morphine is one of the most euphoric drugs known, and via all but the IV route heroin and morphine cannot be distinguished according to studies because heroin is a prodrug for the delivery of systemic morphine. Chemical changes to the morphine molecule yield other euphorigenics such as dihydromorphine, hydromorphone (Dilaudid, Hydal), and oxymorphone (Numorphan, Opana), as well as the latter threes methylated equivalents dihydrocodeine, hydrocodone, and oxycodone, respectively; in addition to heroin, there are dipropanoylmorphine, diacetyldihydromorphine, and other members of the 3,6 morphine diester category like nicomorphine and other similar semi-synthetic opiates like desomorphine, hydromorphinol, etc. used clinically in many countries of the world but also produced illicitly in rare instances.In general, non-medical use of morphine entails taking more than prescribed or outside of medical supervision, injecting oral formulations, mixing it with unapproved potentiators such as alcohol, cocaine, and the like, or defeating the extended-release mechanism by chewing the tablets or turning into a powder for snorting or preparing injectables. The latter method can be as time-consuming and involved as traditional methods of smoking opium. This and the fact that the liver destroys a large percentage of the drug on the first pass impacts the demand side of the equation for clandestine re-sellers, as many customers are not needle users and may have been disappointed with ingesting the drug orally.
Rings A, B and C are the phenanthrene ring system. This ring system has little conformational flexibility...
Two hydroxyl functional groups: a C3-phenolic [hydroxyl group] (pKa 9.9) and a C6-allylic [hydroxyl group],
An ether linkage between C4 and C5,
Unsaturation between C7 and C8,
A basic, [tertiary]-amine function at position 17, [and]
[Five]  centers  of  chirality  (C5,  C6,  C9,  C13  and  C14)  with  morphine  exhibiting  a  high  degree of stereoselectivity of analgesic action." Morphine and most of its derivatives do not exhibit optical isomerism, although some more distant relatives like the morphinan series (levorphanol, dextorphan and the racemic parent chemical racemorphan) do, and as noted above stereoselectivity in vivo is an important issue. Uses and derivatives
Most of the licit morphine produced is used to make codeine by methylation. It is also a precursor for many drugs including heroin (3,6-diacetylmorphine), hydromorphone (dihydromorphinone), and oxymorphone (14-hydroxydihydromorphinone). Most semi-synthetic opioids, both of the morphine and codeine subgroups, are created by modifying one or more of the following:
Halogenating or making other modifications at positions 1 or 2 on the morphine carbon skeleton. The methyl group that makes morphine into codeine can be removed or added back, or replaced with another functional group like ethyl and others to make codeine analogues of morphine-derived drugs and vice versa. Codeine analogues of morphine-based drugs often serve as prodrugs of the stronger drug, as in codeine and morphine, hydrocodone and hydromorphone, oxycodone and oxymorphone, nicocodeine and nicomorphine, dihydrocodeine and dihydromorphine, etc.