Chemical and Physiological Properties
See also: Opioid, Opiate, and MorphinanOpium contains two main groups of alkaloids. Phenanthrenes such as morphine, codeine, and thebaine are the main narcotic constituents. Isoquinolines such as papaverine and noscapine have no significant central nervous system effects, and are not regulated under the Controlled Substances Act. Morphine is the most prevalent and important alkaloid in opium, consisting of 10%–16% of the total, and is responsible for most of its harmful effects such as lung edema, respiratory difficulties, coma, or cardiac or respiratory collapse. Morphine binds to and activates mu opioid receptor in the brain, spinal cord, stomach and intestine. Regular use can lead to drug tolerance or physical dependence. Chronic opium addicts in 1906 China or modern-day Iran consume an average of eight grams of opium daily.
Both analgesia and drug addiction are functions of the mu opioid receptor, the class of opioid receptor first identified as responsive to morphine. Tolerance is associated with the superactivation of the receptor, which may be affected by the degree of endocytosis caused by the opioid administered, and leads to a superactivation of cyclic AMP signaling. Long-term use of morphine in palliative care and management of chronic pain cannot be managed without the possible development of drug tolerance or physical dependence. Many techniques of drug treatment exist, including pharmacologically based treatments with naltrexone, methadone, or ibogaine.
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