Chapter18OpioidAnalgesics.pptVIP

Chapter 21 Opioid-analgesics opium receptor agonists; opium receptor partial agonists; others. [Mechanism of action] Opioid agonists produce analgesia by binding to specific receptors, located primarily in brain and spinal cord regions involved in the transmission and modulation of pain. Receptor types: The major classes of receptors are μ (mu for morphine) delta(δ), and kappa(κ). All are members of the G-protein-coupled family of receptors. Analgesia, as well as the euphoriant, respiratory depressant, and physiologic dependence properties of morphine result principally from actions at mu receptors.Most of the currently available opioid analgesics act primarily at the mu receptor. Opioid Analgesics [Source] Opium is obtained from the opium poppy by incision of the seed pod after the petals of the flower have dropped.The white latex that oozes out turns brown and hardens on standing. This sticky brown gum is opium. It contains about 20 alkaloids, including morphine, codeine etc.The principal alkaloid in opium is morphine,present in a concentration of about 10%. Central effects Peripheral effects 1.Analgesia: Pain consists of both sensory and affective(emotional) components. 2.Sedation and change in mood After a dose of morphine, a patient in pain or an addict experiences a pleasant floating sensation and freedom from anxiety and distress.However,other patients and some normal subjects(not in pain) experience dysphoria rather than pleasant effects after a dose of opioid analgesics. 3.Respiratory depression: All of the opioid analgesics can produce significant respiratory depression by inhibiting the sensitivity of brain stem respiratory center to CO2 . 4.Cough suppression: Opioids directly suppress the cough center in medulla. 5.Emesis Nausea and vomiting are an unpleasant side effect by direct stimulation of CTZ. 6.Miosis: It is valuable in the diagnosis of opioid overdose. 1. Histamine release Causing peripheral arteriolar,venous dilation,and bronchoc