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Pain pathways and Pharmacotherapy
of pain management
Dr. S. Parasuraman,
Faculty of Pharmacy,
AIMST University.
Course: PHARMACOTHERAPEUTICS II
Pain pathways
• Pain has a biologically important protective function.
• Manifestations of pain related to tissue injury including
hyperalgesia, an exaggerated response to a noxious
stimulus, and allodynia, the perception of pain from
normally innocuous stimuli.
• Hyperalgesia and allodynia are the result of changes in
either the peripheral or central nervous systems and
causes peripheral or central sensitization, respectively.
Pain pathways
• The ascending pathways that mediate pain consist of
three different tracts:
– Neospinothalamic tract
– Paleospinothalamic tract
– Archispinothalamic tract
Pain pathways
• Neospinothalamic Tract
Pain pathways
• Paleospinothalamic Pathway
Pain pathways
• Paleospinothalamic Pathway
Pain pathways
• Archispinothalamic Pathway
Pain pathways
• Archispinothalamic Pathway
Sources of PainPain
Somatic Pain
Cutaneous, Superficial
or Peripheral Pain
Deep pain
Visceral Pain
Thalamic Pain
Psychosomatic Pain
Referred Pain
Phantom (illusory)
Pain
Reaction to Somatic
Pain
• Startle response
• Autonomic response
• Behavioral response
Sources of Pain
• Visceral Pain: In the
visceral organs,
nociceptors respond
to mechanical
stimulation such as
pressure, tissue
damage, and
chemical stimulation.
Sources of Pain
• Thalamic Pain: It also called as Dejerive-Roussy
syndrome. Stroke or occlusion in the
thalamogeniculate artery, which supplies the
lateroposterior half of the thalamus, can result in a
thalamic lesion, which is often accompanied by
neurologic conditions several months after the initial
event.
• Neuropathic Pain: It is a sharp, shooting and
devastating pain.
• Psychosomatic Pain: Psychic reaction to pain includes
all the well-known responses to pain such as anguish,
anxiety, crying, depression, nausea and excess
muscular excitability through the body.
Sources of Pain
• Referred Pain: is a painful sensation at a site other
than the injured one. The pain is not localized to the
site of its cause (visceral organ) but instead is localized
to a distant site.
Sources of Pain
• Phantom (illusory) Pain: It is the experience of pain
without any signals from nociceptors.
Pathological classification of pain
• Nociceptive: represents the normal response to
noxious injury of tissues.
• Neuropathic: Pain initiated or caused by a primary
lesion in the somatosensory nervous system.
• Inflammatory: Activation and sensitization of the
nociceptive pain pathway by a variety of mediators
released at a site of tissue inflammation.
Time course: Pain duration
• Acute pain (less than 3 to 6 months duration): Pain
arises from activation of nociceptors for a limited time
and is not associated with significant tissue damage
(e.g., a pin prick).
• Chronic pain (more than 3-6 months): It is prolonged
pain lasting for months or longer that arises from
tissue injury, inflammation, nerve damage, tumor
growth, lesion or occlusion of blood vessels.
• Fibromyalgia: It is characterized by widespread chronic
pain throughout the body, including fatigue, anxiety
and depression.
Overview of inflammatory processes
• Inflammation begins when a stimulus, such as infection,
physical stress, or chemical stress, produces cellular
damage.
Overview of inflammatory processes
• The more important inflammatory mediators are the
eicosanoids, biological oxidants, cytokines, adhesion
factors, and digestive enzymes (proteases, hyaluronidase,
collagenase, and elastase).
• EICOSANOIDS: The pathway initiated by cyclooxygenase
(COX) produces prostaglandins; the lipoxygenase pathway
generates leukotrienes.
Overview of inflammatory processes
• Biological effects of eicosanoids
Overview of inflammatory processes
• Biological Oxidants: The biologically derived oxidants are
potent bacterial killers but are also a major contributing
factor in tissue injury that results from the inflammatory
response. These oxidants include the superoxide anion
(∙O2-), hydrogen peroxide (H2O2), nitric oxide (∙NO),
peroxynitrite (∙OONO∙), hypochlorous acid (HOCl),
peroxidase-generated oxidants of undefined character,
probably the hydroxyl radical (∙OH), and possibly singlet
oxygen (1O2).
• Cytokines: Tumor necrosis factor-α (TNF- α) and
interleukin 1(IL-1) are produced primarily by cells of
the monocyte–macrophage lineage.
Pharmacotherapy of acute pain
• SORT (The Strength-of-Recommendation Taxonomy):
key recommendations for practice
Read more:
Blondell RD, Azadfard M,
Wisniewski AM.
Pharmacologic therapy for
acute pain. Am Fam
Physician. 2013;87:766-72.
Pharmacotherapy of chronic pain
• Treatment algorithm for pharmacotherapy of chronic
non-cancer pain
Read more:
Lynch ME, Watson CP. The
pharmacotherapy of chronic
pain: a review. Pain Res Manag.
2006 ;11(1):11-38.
Thank you

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Introduction to Pain pathology

  • 1. Pain pathways and Pharmacotherapy of pain management Dr. S. Parasuraman, Faculty of Pharmacy, AIMST University. Course: PHARMACOTHERAPEUTICS II
  • 2. Pain pathways • Pain has a biologically important protective function. • Manifestations of pain related to tissue injury including hyperalgesia, an exaggerated response to a noxious stimulus, and allodynia, the perception of pain from normally innocuous stimuli. • Hyperalgesia and allodynia are the result of changes in either the peripheral or central nervous systems and causes peripheral or central sensitization, respectively.
  • 3. Pain pathways • The ascending pathways that mediate pain consist of three different tracts: – Neospinothalamic tract – Paleospinothalamic tract – Archispinothalamic tract
  • 9. Sources of PainPain Somatic Pain Cutaneous, Superficial or Peripheral Pain Deep pain Visceral Pain Thalamic Pain Psychosomatic Pain Referred Pain Phantom (illusory) Pain Reaction to Somatic Pain • Startle response • Autonomic response • Behavioral response
  • 10. Sources of Pain • Visceral Pain: In the visceral organs, nociceptors respond to mechanical stimulation such as pressure, tissue damage, and chemical stimulation.
  • 11. Sources of Pain • Thalamic Pain: It also called as Dejerive-Roussy syndrome. Stroke or occlusion in the thalamogeniculate artery, which supplies the lateroposterior half of the thalamus, can result in a thalamic lesion, which is often accompanied by neurologic conditions several months after the initial event. • Neuropathic Pain: It is a sharp, shooting and devastating pain. • Psychosomatic Pain: Psychic reaction to pain includes all the well-known responses to pain such as anguish, anxiety, crying, depression, nausea and excess muscular excitability through the body.
  • 12. Sources of Pain • Referred Pain: is a painful sensation at a site other than the injured one. The pain is not localized to the site of its cause (visceral organ) but instead is localized to a distant site.
  • 13. Sources of Pain • Phantom (illusory) Pain: It is the experience of pain without any signals from nociceptors.
  • 14. Pathological classification of pain • Nociceptive: represents the normal response to noxious injury of tissues. • Neuropathic: Pain initiated or caused by a primary lesion in the somatosensory nervous system. • Inflammatory: Activation and sensitization of the nociceptive pain pathway by a variety of mediators released at a site of tissue inflammation.
  • 15. Time course: Pain duration • Acute pain (less than 3 to 6 months duration): Pain arises from activation of nociceptors for a limited time and is not associated with significant tissue damage (e.g., a pin prick). • Chronic pain (more than 3-6 months): It is prolonged pain lasting for months or longer that arises from tissue injury, inflammation, nerve damage, tumor growth, lesion or occlusion of blood vessels. • Fibromyalgia: It is characterized by widespread chronic pain throughout the body, including fatigue, anxiety and depression.
  • 16. Overview of inflammatory processes • Inflammation begins when a stimulus, such as infection, physical stress, or chemical stress, produces cellular damage.
  • 17. Overview of inflammatory processes • The more important inflammatory mediators are the eicosanoids, biological oxidants, cytokines, adhesion factors, and digestive enzymes (proteases, hyaluronidase, collagenase, and elastase). • EICOSANOIDS: The pathway initiated by cyclooxygenase (COX) produces prostaglandins; the lipoxygenase pathway generates leukotrienes.
  • 18. Overview of inflammatory processes • Biological effects of eicosanoids
  • 19. Overview of inflammatory processes • Biological Oxidants: The biologically derived oxidants are potent bacterial killers but are also a major contributing factor in tissue injury that results from the inflammatory response. These oxidants include the superoxide anion (∙O2-), hydrogen peroxide (H2O2), nitric oxide (∙NO), peroxynitrite (∙OONO∙), hypochlorous acid (HOCl), peroxidase-generated oxidants of undefined character, probably the hydroxyl radical (∙OH), and possibly singlet oxygen (1O2). • Cytokines: Tumor necrosis factor-α (TNF- α) and interleukin 1(IL-1) are produced primarily by cells of the monocyte–macrophage lineage.
  • 20. Pharmacotherapy of acute pain • SORT (The Strength-of-Recommendation Taxonomy): key recommendations for practice Read more: Blondell RD, Azadfard M, Wisniewski AM. Pharmacologic therapy for acute pain. Am Fam Physician. 2013;87:766-72.
  • 21. Pharmacotherapy of chronic pain • Treatment algorithm for pharmacotherapy of chronic non-cancer pain Read more: Lynch ME, Watson CP. The pharmacotherapy of chronic pain: a review. Pain Res Manag. 2006 ;11(1):11-38.

Editor's Notes

  1. DRG: dorsal root ganglion
  2. Deep Pain : The paleospinothalamic pathway and The archispinothalamic pathway.
  3. http://neuroscience.uth.tmc.edu/s2/chapter07.html#fig7_4
  4. http://neuroscience.uth.tmc.edu/s2/chapter07.html#fig7_4
  5. Ref: http://journal.frontiersin.org/article/10.3389/fcimb.2014.00069/full