Opioid analgesics

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Opioid analgesics

  1. 1. Opioid Analgesics
  2. 2. <ul><li>Strong </li></ul><ul><li>Morphine </li></ul><ul><li>Methadone </li></ul><ul><li>Meperidine </li></ul><ul><li>Moderate </li></ul><ul><li>Codeine </li></ul><ul><li>Oxycodone </li></ul><ul><li>Weak </li></ul><ul><li>Propoxyphene </li></ul><ul><li>Mixed (agonists- antagonists) </li></ul><ul><li>Buprenorphine, nalbuphine </li></ul>
  3. 3. <ul><li>Antagonists </li></ul><ul><li>Naloxone </li></ul><ul><li>Naltrexone </li></ul>
  4. 4. Clinical Uses <ul><li>Analgesia- Fentanyl, morphine </li></ul><ul><li>Cough Supression- Codeine, Dextromethorphan. </li></ul><ul><li>Antidiarrheal- Diphenoxylate, Loperamide </li></ul><ul><li>Acute Pulmonary edema- Morphine </li></ul><ul><li>Anesthesia- Fentanyl </li></ul><ul><li>Opioid Dependence- Methadone </li></ul>
  5. 5. Pharmacokinetis <ul><li>Well absorbed orally </li></ul><ul><li>Morphine, hydromorphone, oxymorpine undergo first-pass metabolism. </li></ul><ul><li>Cross placental barrier and effect fetus, cause respiratory depression, physical dependence in neonates. </li></ul><ul><li>Metabolism: by hepatic enzymes, inactivated by glucuronide conjugates before elimination from kidneys. </li></ul><ul><li>Morphine -6- glucuronide (analgesic) </li></ul><ul><li>Morphine-3- glucuronide ( neuroexcitatory) </li></ul>
  6. 6. Mechanism of action <ul><li>Opioids produce analgesia by binding to specific G protein coupled receptors in brain & spinal cord </li></ul>
  7. 7. Mechanism of action <ul><li>Receptors </li></ul><ul><li>μ , δ , κ receptors. </li></ul><ul><li>All 3 subtypes are involved in antinociceptive and analgesic mechanisms at both spinal and supraspinal levels. </li></ul><ul><li>μ receptors -respiratory depressant+ GI </li></ul><ul><li>δ receptors- development of tolerance </li></ul><ul><li>κ receptors- involved in sedation + GI </li></ul>
  8. 9. <ul><li>Opioid peptides </li></ul><ul><li>β -endorphin, ( μ ,receptors) </li></ul><ul><li>Enkephalins ( δ receptors ) </li></ul><ul><li>Dynorphins ( κ receptors) </li></ul><ul><li>Modulate transmission in brain, spinal cord, adrenal medulla and neural plexus of gut. </li></ul>
  9. 10. <ul><li>All 3 receptors are in high concentration in dorsal horn of spinal cord. </li></ul><ul><li>Direct application of opioid agonists at spinal cord produce regional analgesia. </li></ul><ul><li>Resp. depression, nausea, vomiting, sedation from supraspinal action. </li></ul>
  10. 11. Ionic Mechanisms <ul><li>Presynaptic level close voltage gated Ca+ channels, and reduce transmission. </li></ul><ul><li>Post synpatic level open K+ channels (inhibit post synaptic neurons). </li></ul>
  11. 13. EFFECTS <ul><li>Analgesia </li></ul><ul><li>Most powerful analgesics, </li></ul><ul><li>Morphine, methadone, meperidine, fentanyl, heroin </li></ul><ul><li>Sedation and euphoria </li></ul><ul><li>Respiratory depression </li></ul><ul><li>Action at medulla lead to respiratory depression . </li></ul><ul><li>Antitussive effects </li></ul><ul><li>Suppression of the cough reflex </li></ul><ul><li>Nausea & vomiting </li></ul><ul><li>Activation of chemoreceptor trigger zone </li></ul>
  12. 14. Side Effects <ul><li>GI effects </li></ul><ul><li>Constipation with decreased intestinal peristalsis. </li></ul><ul><li>Smoot muscle </li></ul><ul><li>Cause contraction of billiary billiary tract SM, inc. ureter and bladder tone, red. Uterine tone (prolong labor) </li></ul><ul><li>Miosis </li></ul><ul><li>Tolerence </li></ul><ul><li>Dependence </li></ul>
  13. 15. Toxicity
  14. 16. Treatment of Opioid Poisioning
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