Editing Morphine (section)

==== Addiction ====

[[File:Santiago Rusinol Before the Morphine.jpg|thumb|left|''Before the Morphine'' by [[Santiago Rusiñol]]]]

Morphine is a highly [[addictive]] substance. Multiple studies, including one by ''The Lancet'', ranked morphine/heroin as the #1 most addictive substance, followed by [[cocaine]] at #2, [[nicotine]] #3, [[barbiturates]] at #4, and [[ethanol]] at #5. In controlled studies comparing the physiological and subjective effects of [[heroin]] and morphine in individuals formerly addicted to opiates, subjects showed no preference for one drug over the other. Equipotent, injected doses had comparable action courses, with heroin crossing the [[blood–brain barrier]] slightly quicker. No difference in subjects' self-rated feelings of [[euphoria]], ambition, nervousness, relaxation, or drowsiness.<ref name="martin and fraser" /> Short-term addiction studies by the same researchers demonstrated that tolerance developed at a similar rate to both heroin and morphine. When compared to the opioids [[hydromorphone]], [[fentanyl]], [[oxycodone]], and [[pethidine]], former addicts showed a strong preference for heroin and morphine, suggesting that heroin and morphine are particularly susceptible to abuse and addiction. Morphine and heroin also produced higher rates of euphoria and other positive subjective effects when compared to these other opioids.<ref name="martin and fraser" /> The choice of heroin and morphine over other opioids by former drug addicts may also be because heroin is an ester of morphine and morphine [[prodrug]], essentially meaning they are identical drugs ''in vivo''. Heroin is converted to morphine before binding to the [[opioid receptor]]s in the brain and spinal cord, where morphine causes subjective effects, which is what the addicted individuals are seeking.<ref name="NIDA-2013">{{cite web |url = http://www.nida.nih.gov/infofacts/heroin.html |title = Heroin |author = National Institute on Drug Abuse (NIDA) |date = April 2013 |website = DrugFacts |publisher = U.S. National Institutes of Health |url-status = dead |archive-url = https://web.archive.org/web/20051130022758/http://www.nida.nih.gov/Infofacts/heroin.html |archive-date = 30 November 2005 |access-date = 29 April 2008 }}</ref>