Chapter 9: Opioid Analgesics

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• Chapter 9 Opioid Analgesics
• Presented by
• Steffani and Katie

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• Location of opioid receptors in the brain and in
  the brain stem
• Thalamus
• Brain Stem
• Limbic System

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• How are pain impulses modulated as they enter the
  spinal cord?

• The pain impulses can be modulated by one of 2
  pathways by activating pain-inhibitory systems.
  Both systems activate norepinephrine and
  serotonin releasing neurons in the spinal cord
  which inhibits the release of transmitters for
  pain neurons.

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Substance P

• A neuropeptide (amino-acid chain) that is a
  pain-signaling neurotransmitter.
• It is influenced by narcotic analgesics by
  inhibiting the release of Substance P
  presynaptically.

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Effects of Endorphins

• To inhibit the release of transmitters from
  primary afferent (nociceptive) pain neurons.

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What is?

• Opioid Agonist Drug that has an affinity for
  cell receptors to induce changes in the cell
  characteristics of the natural ligand for that
  receptor. Example Morphine

• Opioid Antagonist Drug that has an affinity
  for the receptor but, once attached, has no
  effect other than to BLOCK the receptor from the
  drugs that DO cause an effect. Example Naloxone

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What is?

• Mixed Agonist-antagonist Drug that produces an
  agonist effect at one receptor and an antagonist
  effect at another receptor. These are useful in
  treating opioid dependency because they limit
  withdrawal symptoms to some degree.
• Example Nubain

• Partial Agonist Drug that binds to opioid
  receptors but has a low intrinsic activity (low
  efficacy). Example Ultram

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Why Misuse or Abuse Opioids?

• Addiction is reinforced by the positive physical
  feelings (euphoric state, strong feeling of
  well-being and contentment, and lack of concern).
• Provides user with an experience that the brain
  equates with profoundly important events like
  eating, drinking and sex.
• Becomes an acquired drive state that permeates
  all aspects of human life. (See page 271)

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Naloxone and Naltrexone

• Both are pure opioid antagonists.
• However, naloxone is the prototype antagonist.
  It must be given intravenously and has a brief
  duration of effectiveness (needs to be
  re-injected at short intervals).
• Naltrexone is different in that it is orally
  administered and has a longer duration of
  effectiveness.
• Naltrexone is indicated for use in the treatment
  of alcohol abuse.

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Handling and Treating Opioid Dependency

1. RAAD Rapid, Anesthesia-aided Detoxification
   Administering an opioid antagonist while patient
   is under general anesthesia. This procedure
   cycles at which time the withdrawal symptoms are
   blunted (the idea is to detoxify a patient while
   unconscious).

• 2. Use naltrexone, methadone or LAAM (levo-alpha
  acetylmethadol) to reduce opioid cravings paired
  with supportive psychotherapy to address
  underling causes of addiction and prevent
  relapse. Also, psychotherapy is needed to treat
  comorbid psychological disorders.

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• Thoughts for and against the existence of
  endogenous opioid peptides (endorphins) that
  serve as natural opioids.
• We believe they exist as natural analgesics that
  dampen pain and influence emotions.
• Katie personally experienced this effect during
  distance running and childbirth.

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Buprenorphine

• A semisynthetic, partial agonist opioid with long
  lasting analgesic properties.

• It has a potential use as a substitute for
  methadone or a step down drug from methadone for
  the detoxification and maintenance of opioid
  users.

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• Options in the pharmacological management of
  opioid withdrawal and the prevention of relapse
• Data support lifelong opioid maintenance as a
  treatment option since the rate-of return to
  illicit opioid use is significant despite
  treatment interventions.