More than 20 chemically distinct opioid drugs are in clinical use throughout the world. In the developed countries, the opioid drug most frequently associated with abuse and dependence is heroin; a drug that is not approved for therapeutic purposes in the United States. These drugs are all prototypical-opioid receptor agonists and all produce similar subjective effects. The patterns of use and some aspects of opioid toxicity are powerfully influenced, however, by the route of administration and the metabolism of the specific opioid, as well as by the social conditions that determine its price and purity and the sanctions attached to nonmedical use. » Read more…