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Analgesics

Analgesics. Opioid analgesics Synthetic opioid analgesics Other analgesics. General Considerations. Pain ( 疼痛 ) ： 躯体痛－快痛，慢痛 内脏痛 神经性痛 Analgesia ( 镇痛 ) ： 选择性抑制疼痛感觉， 不影响意识和其他感觉. The perception of somatic pain.

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Analgesics

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  1. Analgesics • Opioid analgesics • Synthetic opioid analgesics • Other analgesics

  2. General Considerations • Pain (疼痛)： • 躯体痛－快痛，慢痛 • 内脏痛 • 神经性痛 • Analgesia (镇痛)： • 选择性抑制疼痛感觉， • 不影响意识和其他感觉

  3. The perception of somatic pain

  4. Peripheral mechanisms of pain

  5. Thalamus Conduction pathways of pain

  6. Cortical locations of pain

  7. Measurement of pain

  8. The fMRI imaging of pain

  9. General Considerations • Classification of analgesics： • Opioid analgesics (centrally acting) • Opiates • Synthetic agents • Antipyretic, analgesic, and anti-inflammatory drugs (peripherally acting) • aspirin, indomethacin • Other drugs (for special types of pain) • Carbamazepine, atropine, etc.

  10. A.Opioid Analgesics Morphine 吗啡 A B D C Morphine 吗 啡 Heroin 海洛因

  11. Morphine: • Morphus,the Greek god of dreams

  12. A.Opioid Analgesics • 1. Pharmacological effects • (1) Mechanisms of actions • Acting on central opioid receptors •  receptors •  receptors • δ receptors

  13. Peripheral mechanisms of morphine actions

  14. Central mechanisms of morphine actions

  15. A.Opioid Analgesics • (2) Central nervous system effects • A. Analgesia：maximal analgesic efficacy； • relieving unpleasant sensation; • euphonia and potential of dependence • B. Depression of respiration: • reducing the sensitivity of respiratory center to CO2 • C. Depression of cough reflex • D. Other central effects: miosis, emesis

  16. A.Opioid Analgesics • (3) Cardiovascular effects • A. Postural hypotension： • Releasing histamine; depressing CVS centers • B. Increase of intracranial pressures： • Respiratory depression  brain CO2 increase •  vasodilatation in the brain

  17. A.Opioid Analgesics • (4) Effects on smooth muscles • A. GI tract： • Contispation: increasing resting tone of smooth muscles and sphincters, decreasing propulsive peristalsis and secretions; • Biliary tract：Oddi’s sphincter contraction, increasing the pressure in the biliary tract • B. Respiratory tract：bronchoconstriction • C. Urinary tract：increasing vesical sphincter tone  urinary retention • D. Uterus

  18. A.Opioid Analgesics • (5) Other effects • A. Immune depression • B. Endocrine effects

  19. A.Opioid Analgesics • 2. Clinical uses • (1) Analgesia • the pain of high intensity and the pain of terminal illness • Cautions: • a) obscure the symptoms and the progress of the disease; • b) dependence or addiction; • c) biliary colic: combined with atropine • d) not used for long-term if no clear indications

  20. A.Opioid Analgesics • (2) Cardiac asthma (acute left ventricular failure) • As an adjuvant treatment • A. Vasodilatation: after-load  • B. Sedation: anxiety  • C. Respiratory depression: breathing slowly and deeply • (3) Diarrhea

  21. A.Opioid Analgesics • 3. Adverse effects • (1) Side effects • (2) Tolerance and dependence • psychological and physic dependence: addiction • withdrawal syndromes or abstinance syndromes

  22. A.Opioid Analgesics • (3) Acute intoxication • coma, respiratory depression, • hypotension, pinpoint pupils • reversed by naloxone, an opioid receptor antagonist • (4) Contraindications • labor and lactation; • bronchial asthma and cor pulmonal; • increased intracranial pressures; • severe hepatic damage

  23. A.Opioid Analgesics Codeine 可待因 • Analgesia; central antitussive

  24. B.Synthetic Analgesics Pethidine 哌替啶 Dolantin 度冷丁

  25. Structures of natural opioid (morphine) and synthetic analgesics (pethidine) 哌啶环中的叔氮 与叔氮相隔两个碳原子的季碳 与季碳相连的苯环 Morphine Pethidine

  26. B.Synthetic Analgesics • Pethidine • 1. Pharmacological effects • Similar to morphine but ineffective for cough and diarrhea, and its metabolite normeperidine has central stimulant effect • 2. Clinical uses • analgesia; • cardiac asthma; • preanesthetic medication or artificial hibernation; • 3. Adverse effects • similar to morphine, convulsion (overdose)

  27. B.Synthetic Analgesics • Fentanyl （芬太尼） • high efficacy • combined with droperidol: neuroleptanalgesia • Methadone （美沙酮） • orally effective • long-acting • used for displacement in heroin or morphine detoxication

  28. B.Synthetic Analgesics • Pentazocine （喷他佐辛, 镇痛新） • κ receptor agonist / μ receptor partial agonist; • non-narcotic analgesic drug • psychotomimetic effects: anxiety, nightmare, hallucinations • Tramadol （曲马朵） • Relatively weak efficacy and dependence

  29. 附： 阿片受体拮抗药 Opioid receptor antagonists • Naloxone （纳洛酮） • Naltrexone （纳曲酮） • Antidotes for acute intoxication of opioids • Treatment of shock and other diseases

  30. Summary of opioid receptor ligands

  31. C.Other Analgesics • Rotundine （罗通定） • dl-Tetrahydropalmatine （延胡索乙素） • chronic pain • sedative effects • no addiction

  32. 附：癌痛的镇痛治疗 • 三级止痛阶梯治疗： • 轻度：解热抗炎镇痛药 • 中度：加用或改用弱阿片药 • 重度：强阿片药 • 应用原则： • 尽可能口服用药 • 按时规则用药，剂量个体化 • 辅助措施

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