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PR3136 > NARCOTIC (OPIOID) ANALGESIC > Flashcards

NARCOTIC (OPIOID) ANALGESIC Flashcards

1
Q

Raw opium contains _

A

20 alkaloids (aka opiates)

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2
Q

4 main classes of opioids

A
  1. Phenanthrenes
  2. Benzylisoquinolines
  3. Tetrahydroisoquinolines
  4. Cryptopines
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3
Q

Phenanthrenes

A
  1. Morphine (10%)
    - strong opioid
  2. Codeine (0.5%)
    - weak opioid
  3. Thebaine (0.2%)
    - used for the synthesis of naloxone (opioid antagonist)
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4
Q

Endogenous opioid peptides (3)

A
  1. Beta-endodorphins
    - from preproopiomelanocortin (POMC)
    - 30 aa
  2. Enkephalins
    - from preproenkephalin
    - pentapeptides (5)
  3. Dynorphin
    - from preprodynorphin
    - 18-20 aa

Last time known as endorphins, now called opioids peptides

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5
Q

Factors that can affect pain perception

A
  1. Attitude
  2. Mood
  3. Physical exercise
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6
Q

Transmission of pain

A

Pain to brain

  1. Primary Afferent Neuron (A delta- / C-fibre)
  2. Spinothalamic tract

Brain to pain
1. Efferent Neuron (modulate pain)

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7
Q

MOA of pain modulation

A
  1. Inhibit the propagation of pain signals
  2. Alter emotional perception of pain
  3. Elevate pain threshold
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8
Q

Sites of opioid receptors regulating pain (3)

A
  1. Peripheral nociceptive terminals
    - peripheral analgesia
  2. Spine
    - spinal analgesia
  3. Brain
    - supraspinal analgesia
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9
Q

3 major opioid receptors

A
  1. mu
  2. delta
  3. kappa

all G-protein coupled receptors

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10
Q

Euphoria vs Dysphoria

A

Euphoria
- intense happiness and excitement

Dysphoria
- very unhappy, uneasy or dissatisfied

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11
Q

Miosis vs Mydriasis

A

Miosis

  • pupil constriction
  • pinpoint pupil
  • ADR of opioid analgesic
  • signs of opioid overdose (short term)

Mydriasis
- pupil dilation

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12
Q

Individual dosing features (3)

A
  1. Elderly patients require lower dose to achieve effective pain relief than younger patients
  2. Neuropathic pain require higher doses than nociceptive pain
  3. Lower doses are usually required for continuous maintenance of pain relief than administration only in response to recurrence of pain
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13
Q

Dosing to effect considerations (3)

A
  1. Start with low dose and carefully titrate until adequate level of analgesia is obtained or until persistent and unacceptable side effects warrant a re-evaluation of therapy.
  2. Failure of a least partial analgesia with incremental dosing in opioid-naive patient may indicate that the pain syndrome is unresponsive to opioid therapy
  3. Some patients with chronic pain, opioids do not exert an appreciable analgesic effect until a threshold dose has been achieved
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14
Q

Clinical uses of opioid agonists (4)

A
  1. Analgesia
    - morphine
    - codeine
    - pethidine (used in labor)
  2. Adjunctive anaesthetic
    - fentanyl
  3. Cough-suppressant/anti-tussive
    - codeine
  4. Anti-diarrhoeal
    - diphenoxylate
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15
Q

Strong opioid agonist (4)

A
  1. Morphine
  2. Methadone
  3. Fentanyl
  4. Pethidine (Meperidine)
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16
Q

Morphine

A
  • strong opioid agonist
  • strong mu, weak delta & kappa
  • maximum analgesic efficacy
  • high liability for addiction/abuse
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17
Q

Methadone

A
  • strong opioid agonist
  • strong mu, no significant delta & kappa
  • long acting (plasma half life >24h)
  • high liability for addiction/abuse
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18
Q

Fentanyl

A
  • strong opioid agonist
  • strong mu, no significant delta & kappa
  • short acting (hence adjuvant anaesthetic)
  • high liability for addiction/abuse
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19
Q

Pethidine (Meperidine)

A
  • strong opioid agonist
  • strong mu, weak delta & kappa
  • shorter duration of action than morphine (esp in neonates, hence used in labour)

ADR :

  • restlessness > sedation
  • N-demethylated in the liver to give norpethidine (hallucinations & convulsive)
  • anti-muscarinic (dry mouths & blur vision but no miosis & less spasm of smooth muscle)
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20
Q

Moderate opioid agonists (2)

A
  1. Codeine

2. Tramadol

21
Q

Codeine

A
  • moderate opioid agonist
  • weak mu & delta, no kappa
  • low maximum analgesic efficacy
  • 10% converted to morphine/dihydromorphine by demethylation.
    10% of ppl shows reduced analgesic efficacy due to lack of demethylating enzymes
  • moderate liability for addiction/abuse
22
Q

Tramadol

A
  • weak mu
  • weak 5-HT & noradrenaline reuptake inhibitor (SNRI)
  • Ondansetron (5-HT antagonist), reduce analgesic efficacy of tramadol - shows tramadol is 5-HT agonist to cause analgesic effect?
23
Q

ADR of opioid agonists (9)

A
  1. Respiratory depression
  2. N/V
  3. Drowsiness
  4. Constipation
  5. Miosis (pinpoint pupil)
  6. Urinary retention
  7. Postural hypotension & bradycardia
  8. Immunosuppression
  9. Histamine release (morphine)
24
Q

Respiratory depression

A
  • actions in nucleus tractor solitarius & nucleus ambiguus
  • reduce response to CO2 & H+
  • suppress voluntary breathing

should not occur at normal therapeutic doses but can be lethal in :

  1. overdosage
  2. respiratory disease
  3. hepatic dysfunction
  4. combination with other CNS depressants
  5. young children
25
Q

Can opioid agonists be used in infants?

A

No.

26
Q

N/V

A
  • due to actions on the chemoreceptor trigger zone (CTZ) of medulla
  • reduces with repeated doses
27
Q

Constipation

A
  • due to reduced GI motility (esp w chronic use)
28
Q

Miosis

A
  • pinpoint pupils
  • actions in oculomotor nucleus
  • pinpoint pupil is a diagnostic feature of opioid overdose. HOWEVER, if hypoxia occurs due to respiratory depression, mydriasis of eyes follows
29
Q

Urinary retention

A
  • increased bladder sphincter muscle tone (esp males with prostatic hypertrophy)
30
Q

Postural hypotension & bradycardia

A
  • actions in cardioregulatory nuclei in the medulla
31
Q

Immunosuppressant

A
  • due to long-term use

- effect on CNS system on immune system

32
Q

Histamine release from mast cells by morphine

A
  1. urticaria & itching
  2. bronchoconstriction
  3. hypotension from vasodilation

Hence, morphine should be used in caution in asthmatic patients

33
Q

Tolerance

A
  • less effective after prolong use

- dose escalation required

34
Q

Physical dependence

A
  • physiological dependence
  • stopping the drug lead to physical withdrawal symptoms
    eg joint pain, rhinorrhea, lacrimation
    anxiety, irritability, chills, hot flushes, n/v, abdominal cramps & diarrhea
35
Q

Addiction

A
  • psychological craving
  • compulsive use
  • loss of control over use
36
Q

Addiction and tolerance can lead to _

A

opioid overdose

37
Q

Opioid antagonists (3)

A
  1. Naloxone
  2. Naltrexone
  3. Nalmefene
  • strong mu antagonist
  • used to conteract opioid overdose
  • use in caution with patients with opiate dependency as they can precipitate potentially fatal withdrawal symptoms
38
Q

Naloxone

A
  • short acting
  • IV
  • made from thebaine
39
Q

Naltrexone

A
  • long acting

- PO

40
Q

Nalmefene

A
  • long acting

- IV

41
Q

Pethidine ADR (3)

A

ADR :

  1. Restlessness > sedation
  2. N-demethylated in the liver to give norpethidine (hallucinations & convulsive)
  3. Anti-muscarinic (dry mouths & blur vision but no miosis & less spasm of smooth muscle)
42
Q

Morphine ADR (3)

A

Histamine release resulting in :

  1. Urticaria & itching
  2. Bronchoconstriction (use in caution in asthmatics)
  3. Hypotension due to vasodilation
43
Q

Morphine should be used in caution in patients with __

A

Asthma

44
Q

Opioid antagonists should be used in caution in patients with __

A

Physical dependency

- use of opioid antagonist can precipitate potentially fatal withdrawal syndrome

45
Q

Respiratory depression results in __ and __

A
  1. Reduce response to CO2 and H+ stimulation

2. Suppress voluntary respiration

46
Q

Respiratory depression should not occur at normal therapeutic doses unless __ (5)

A
  1. Overdosage
  2. Respiratory disease
  3. Hepatic dysfunction
  4. Concurrent use with other CNS depressants
  5. Young children
47
Q
  1. Codeine to morphine/dihydromorphine
    vs
  2. Pethidine to norpethidine
A
  1. Demethylation

2. N-demethylation

48
Q

Tramadol pharmacological activities

A
  1. Moderate opioid agonist

2. Weak SNRI effect

PR3136 (19 decks)

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