Opioid analgesics and antagonists 2010Bb

Opioid analgesics and antagonists 2010Bb - OPIOID...

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OPIOID ANALGESICS AND ANTAGONISTS Dr. Larry Grupp Department of Pharmacology University of Toronto
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LEARNING POINTS Some background Opiate receptors Pain and analgesia Opiates and pain Effect of opiate administration Opiate agonists and antagonist Tolerance, dependence, withdrawal
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Opium Natural product from poppy plant papaver somniferum Sap from flower pod Effects known for >5,000 years Chewed or smoked Greeks and Romans used opium to produce sleep , and ultimately as a panacea for all ills: Hippocrates, Pliny, and Galen
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Opium Arab traders took it to India and China British control of opium production in India Usage in Britain climbed during the 1800s Harrison Narcotics Act, 1914 taxing and limiting use in USA Heroin banned in 1924
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Definitions Opioids - all naturally occurring and synthetic substances which bind to opioid receptors in brain and periphery Opiates - drugs derived from opium Analgesia - absence of the sense of pain without loss of consciousness
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OPIATE RECEPTORS Mu 1 1 ) analgesia, euphoria Mu 2 2 ) constipation, respiratory depression Kappa spinal analgesia, dysphoria Delta analgesia thru the endorphin, enkephalin and dynorphin system
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Opiate Receptors Mu (μ) Mu receptors located in: all pain-control areas of the brain and spinal cord P eriaqueductal gray in midbrain S pinal trigeminal nucleus C audate nucleus T halamic nucleus in the respiratory control centers, and nucleus accumbens. Mu receptors respond to exogenous opiate drugs such as morphine and fentanyl Mu receptors respond to endogenous opioids such as enkephalin or endorphin μ 1 supraspinal analgesia, euphoria, miosis, prolactin release μ 2 spinal analgesia, respiratory depression, constipation, physical dependence
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Definitions Spinal analgesia: Suppression of pain by analgesic drugs into the space around the spinal cord . e.g. epidural At the level of the spinal cord, opiates interfere with the transmission of the pain messages between neurons and therefore prevent them from reaching the brain.
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Definitions Supraspinal analgesia: Suppression of pain by drugs in the brain itself. allow a person to know he or she is experiencing pain and that it is unpleasant. Opiates also act in these brain regions, but they don't block the pain messages themselves change the subjective experience of the pain
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Opioid receptors Kappa κ Kappa receptors are located in: basal ganglia nucleus accumbens ventral tegmentum cortex hypothalamus periaqueductal gray spinal cord respond to mixed agonist-antagonists, like pentazocine (Talwin) and endogenous Dynorphin A mixed ag-antag has affinity for two or more types of opioid receptors and blocks opioid effects on one receptor type while producing opioid effects on a second receptor type κ 1 spinal analgesia, hypothermia, sedation
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Opioid analgesics and antagonists 2010Bb - OPIOID...

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