PHAR: Opioid Analgesics Flashcards Preview

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Flashcards in PHAR: Opioid Analgesics Deck (16):
1

Most systemic analgesics are based off of what two drug categories?

  • Opioids.
    • Active inhibitory systems.
  • Salicylates.
    • Inhibit prostaglandin synthesis.
      • COX inhibitors, NSAIDs.

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2

Describe endorphins and their mechanism of action.

Endogenous opioid peptide.

  • Endogenous = produced within the body.
  • Peptide that binds to opioid receptors in the brain.

 

Note: similarity in structure between opioid drug morphine and endogenous opioid peptide enkephalin.

 

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3

  • What are the structure of the opioid receptors
  • What are the three classes of receptors?

  • Around 400 amino acids.
    • Around 7 transmembrane domains.
  • Classes: µ (mu), κ (kappa), δ (delta) → 90% of amino acids identical.
    • Mu → M → morphine.

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4

  • Which two components of the CNS contain opioid receptors?
    • Which receptors?

 

  • Which opioid receptor is found in the PNS?

 

  • Brain.
    • Brain stem (relevant for analgesia) (μ).
    • κ more prelevant in other components such as the limbic system (associated with abuse and addiction).
  • Dorsal horn of the spinal cord.
    • Presynaptic (relevant for analgesia) (μ > δ).

 

  • ​Periphery.
    • On nociceptive fibres.
    • Drugs won’t cross blood-brain barrier

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5

  • Activation of the μ receptor leads to what side effects?

  • Supraspinal analgesia.
  • Miosis.
    • Excessive pupil constriction.
  • Euphoria.
  • Respiratory depression.
    • Can cause death.
  • Physical dependence.

6

  • Name three μ agonists.
  • Name one mixed agonist-antagonist.
  • Name two opioid receptor antagonist.
  • Name some of their benefits.

​AGONIST

  • Morphine.
  • Methadone.
  • Buprenorphine.
    • Less respiratory depression.

MIXED AGONIST/ANTAGONIST

  • Nalbuphine.
    • μ antagonist, κ agonist.

ANTAGONISTS

  • Naloxone.
    • Fast-acting, potent antagonist to stop respiratory depression.
  • Naltrexone.
    • Long-acting, used for treatment of drug addiction.

 

 

 

 

7

List eight adverse side effects of opioids.

  • Respiratory depression.
    • Worst side effect, potentially fatal.
  • Nausea/vomiting.
  • Constipation.
  • Sedation.
  • Hallucinations.
  • Confusion.
  • Physical dependence and tolerance. 
  • Psychological dependence/abuse.

8

  • Define tolerance and physical dependence in the context of opioids.
  • Differentiate them from addiction.

  • Tolerance = PHYSIOLOGICAL TERM.
    • Physiological adaptation to the chronic effects of opioids.
    • Body adapts so dose needs to be increased.
    • Tolerance can disappear very quickly.
    • Doesn't imply addiction.
  • Physical dependence = withdrawal symptoms when you stop taking the drug.

    • Nausea, vomiting, anorexia, diarrhoea, sweating, shivering, anxiety, depression.

    • Nearly universal with opioid use longer than one week.

    • Can be avoided by tapering opioid gradually.

  • Addiction = Compulsive use of a substance despite harm.

    • Tolerance and physical dependence with opioids are not indicative of addiction.

    • Effects compounded by tolerance and physical dependence.

9

Define opiophobia.

Customary underutilisation of opioids for unfounded fears of creating dependence and addiction.

10

What are the issues associated with chronic pain states and the use of opioid treatment?

  • Other factors need to be addressed that opioids may not necessarily address → opioids can be the 'easy way out' without addressing these other factors.
    • Suffering.
    • Dysfunction.
    • Mood states.
    • Psychosocial factors.
    • Dependence on health system.
  • Opioids activate glia cells → more pain (opioid-induced hyperalgesia).

  • Can lead to abuse.

  • Useful in only a small subpopulation of patients.

11

  • What components are required for opioids to be prescribed?
  • Give an example of pain where opioids WOULDN'T be prescribed.

  • A full assessment process looking at/including:
    • A pain diagnosis.
    • Mental health.
    • Alcohol/drug dependency.
    • A trial of non-opioid analgesia + non-drug treatment.
    • Corroborating history from other health professionals.
  • Never prescribe opioids for headaches.

    • Makes it worse.

    • Also fibromyalgia and non-specific lower back pain.

12

What are the four elements to review the pain diagnosis and comorbid conditions?

  • Analgesia.
  • Activity.
  • Adverse effects.
  • Aberrant behaviour.

13

  • Codeine isn't an opiate, but metabolises in the liver to produce _____.
    • Which enzyme is used in this process?
    • What can happen in the case of fast metabolisers?
  • Codeine is a weak opioid, and its efficacy hasn't always been proven. Why is it still used? (2 points)

  • Codeine isn't an opiate, but metabolises in the liver to produce morphine. (codeine = prodrug)
    • CYP2D6.
    • Amount of morphine you produce is entirely dependent on the demethylation effects of CYP2D6, an enzyme that is lacking in some patients.
    • Fast metabolisers → can die from 'normal' doses of codeine.
  • Acceptable to patients, and convenient for prescribers.

 

14

  • What category of opioid does tramadol fall under, strong, atypical, or weak opioid?
    • Why does this make it suitable for clinical practice.
  • What is it's mechanism/s of action?

  • Tramadol = atypical opioid.
    • As pure opioid effects are lower, less risk of addiction.
  • Three mechanisms of action.
    • Opioid effect: μ-opioid receptor agonist.
    • SRI: serotonin reuptake inhibitor.
    • NRI: noradrenaline reuptake inhibitor.

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15

  • When is tramadol recommended/advisable?
  • What are some common side effects?

 

  • Useful in situations where one wants to avoid or reduce opioid adverse effects like:
    • Respiratory depression.
    • Constipation.
    • Abuse.
    • Sedation/confusion
  • Neuropathic pain.

 

SIDE EFFECTS

  • Nausea.
  • Vomiting.
  • Confusion.
  • Interaction with other serotonergic drugs (antidepressants).
    • Don't mix serotonergic drugs with tramadol.

16

  • What are the mechanism/s of action of tapentadol?
  • How does it differ from tramadol?
  • How does it compare with morphine (and opioids in general) in terms of analgesia?

  • Atypical opioid.
  • Dual mechanism:
    • MOR (mu opioid receptor agonist).
    • NRI (noradrenaline reuptake inhibitor).
  • No SRI effects, so nasty serotonin effects removed.
  • Equianalgesic.
    • But 1/18th of morphine activity on opioid receptor.

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