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MBBS II HNNS > L16 - Narcotic Analgesics > Flashcards

L16 - Narcotic Analgesics Flashcards

1
Q

Local anesthetic can be used for analgesia of diffus pain. T or F?

A

False

Not used for analgesia especially diffuse, generalized pain except in dental surgery

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2
Q

Brief overview of the nociceptive pathway?

A

Nociceptor in skin/ deep tissue

> > Primary afferent neuron

> > Dorsal root ganglion

> > synapse with 2nd order neuron at dorsal horn (laminae I, II, V)

> > Brainstem, Thalamus

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3
Q

Function of endogenous opioid? List 2 instrinsic opioid peptides?

A

Descending modulation of nociceptive information

1) β-endorphin (precursor = pro-opioimelanocortin (POMC))
2) Enkephalin

Release from from pituitary act on opioid receptors in:

  • Periaquaductal grey
  • Locus ceruleus
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4
Q

Classes of opioids according to chemical structure? MMMP

A
  • Morphine derivatives
  • Methadone and propoxyphene
  • Mixed agonist antagonist (partial agonist)
  • Phenylpiperidines
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5
Q

Classes of opioids according to clinical use?

A

1) Strong
– Morphine derivatives,
– Phenypiperidine (pethidine, fentanyl & derivatives)

2) Mild
– Partial agonists,
– dextropropoxyphene

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6
Q

List some morphine derivatives?

A
  • Morphine
  • Morphine-6β-glucuronide
  • Codeine (methylated morphine)
  • Heroin (di-acetyl Morphine)
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7
Q

List some fentanyl derivatives?

A
  • Fentanyl
  • Remifentanil (ultra-potent, ultra short-acting)
  • Alfentanil
  • Sufentanil
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8
Q

Subclasses of Phenylpiperidine?

A

1) Pethidine

2) Fentanyl + derivatives

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9
Q

Pharmacokinetics of Morphine? Metabolism, solubility, excretion…etc

A

Metabolism:

  • Lipid soluble, can cross BBB
  • Tend to accumulate in body, so Context- sensitive
  • Metabolized in liver by glucuronidation into mostly Morphine-6β-glucuronide (water soluble)
  • Excreted by Kidney
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10
Q

Difference in duration of action and potency between Morphine and Morphine-6β-glucuronide?

A

Morphine-6β-glucuronide = More opioid receptor acitivity, Longer lasting effect as active metabolite , more water soluble than morphine

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11
Q

Metabolism, onset and potency of codeine?

A

Codeine = prodrug

> > demethylated in liver
slower onset, less euphoric

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12
Q

Pethidine metabolism pathway?

A

Major:
Esterase + Conjugation of Pethidine for renal excretion

Minor:
Converted to norpethidine intermediate, which is NEUROTOXIC

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13
Q

What precautions are taken when admin. Pethidine?

A

Minor Intermediate Norpethidine is neurotoxic&raquo_space; neural seizure, convulsion

Patients at risk: normal liver function but bad kidney function

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14
Q

Is the gap between ED95 and LD05 of Narcotic analgesics large or small?

A

ED95 and LD05 overlaps

Absolutely minimal therapeutic window&raquo_space; easy to OD

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15
Q

What does the gap between ED95 and LD05 signify?

A

Therapeutic window of a drug

Large gap = large window

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16
Q

Rank the Fentanyl derivatives in terms of elimination half life.

A

Increasing time:

Remifentanil&raquo_space; Alfentanil&raquo_space; Sulfentanil&raquo_space; Fentanyl

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17
Q

Rank the Fentanyl derivatives in terms of relative potency.

A

Decreasing potency:

Sufentanil
Fentanyl
Remifentanil
Alfentanil

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18
Q

Compare Alfentanil and Sufentanil in terms of Onset, Ease of titration and euphoria strength?

A

1) Alfentanil: crosses BBB quickly (faster onset, less time lag):
stronger euphoria, easier to titrate
(Remifentanil also rapid)

2) Sufentanil: crosses BBB slowly (time lag):
lower peak brain concentration = weaker euphoria, harder to titrate (may be overdosed)

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19
Q

Explain the mechanism of Context-sensitivity.

A

Context sensitive = t1/2 of opioid depends on the duration of admin/ infusion

i.e. Continuous infusion by IV leads to higher t1/2 than expected, drug stays in CNS for longer and exert more effect

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20
Q

What is the solubility and non-ionized fraction of most clinically used opioids?

A

To cross BBB effectively:

High lipid solubility
Non-ionized fraction at body pH

21
Q

Relate onset time of opioid to addictive potential. Give an opioid with rapid onset.

A

Faster onset time = faster diffusion into CNS = Higher addictive potential due to stronger effect/ euphoria

Remifentanil = rapid onset

22
Q

Relate the change in plasma concentration of opioids to the EEG response.

A

EEG reflects drowsiness

Rise in plasma concentration of opioid matches closely with sharp increase in EEG = little time between infusion and patient drowsiness

23
Q

Give one opioid that is easy to titrate and explain why?

A

Alfentanil

Plasma concentration closely reflects dosage administered and EEG response

Almost immediate effect of drowsiness with no time lag

24
Q

Give examples of most context-sensitive and context-insensitive opioids.

A

Most sensitive = Fentanyl

Least sensitive = Remifentanil
(regardless of duration of infusion, t1/2 is the same after withdrawal)
Very useful in operating room

25
Q

Example of partial agonist narcotic analgesic?

A

Tramadol

26
Q

Indication of Tramadol?

A

For patients with mild-moderate pain, short-moderate term use

27
Q

D/D interaction of Tramadol and MoA?

A

MoA = Increases serotonin, catecholamine levels
by blocking reuptake&raquo_space; serotonin syndrome

D/D = Serotonin- reuptake inhibitor antidepressants (e.g. tricyclics, SSRI)

28
Q

Give an example of Propoxyphene and associated commercial names. Is it still used?

A

Dextropropoxyphene

Commercial names:
Doloxene
Dologesic (dextropropoxyphene + paracetamol)

Associated with arrhythmia = withdrawn by FDA = no longer available

29
Q

Indication of Methadone?

A

Longest acting&raquo_space; for chronic, stable pain

Slow onset&raquo_space; Do not notice euphoria

Indicated for opioid abuse - helps quitting addiction

30
Q

Explain the D/D interaction between certain types of opioids?

A

Strong opioids and mixed agonists/ mild opioids

Mild opioids or mixed agonist opioids can displace strong opioids from receptors&raquo_space; Paradoxically reduce effect

31
Q

Explain the D/D interaction between certain types of opioids?

A

Strong opioids and mixed agonists/ mild opioids

Mild opioids or mixed agonist opioids can displace strong opioids from receptors&raquo_space; Paradoxically reduce effect

32
Q

Which type of opioid receptors are most activated by narcotic opioids?

A

μ receptors

μ1 and μ2

33
Q

Compare the analgesia produced by Opioids acting on μ1 and μ2 receptors.

A

μ1 = Supraspinal + peripheral analgesia
(+ Prolactin release, Ach release in hippocampus and Feeding)

μ2 = Spinal analgesia + Respiratory depression
(+ Gastrointestinal transit + Dopamine release by nigrostratial neurons + Feeding)

34
Q

List all route of admin of opioids?

A 
 Intravenous 
 Oral 
 Indwelling subcutaneous cannula
 Transmucosal
 Intraspinal injection 
 Ventilatory system
35
Q

Indication for Indwelling subcutaneous cannula admin of opioids?

A

 Lipid-soluble = well absorbed

 When oral is not feasible (e.g. nausea, vomiting) i.e. terminally ill or dysphagia

36
Q

Indication for transmucosal admin of opioids?

A

 For kids
 Absorbed through oral mucosa
 Can cause overdose, addiction
 dangerous

37
Q

Advantages of intraspinal injection of opioids?

A

Bypass BBB

Very high bioavailability

Very low dose needed compared to IV/ oral = reduce side effects

38
Q

List acute side effects of opioids?

A
  • Sedation
  • Nausea/ vomit
  • Respiratory depression (lethal)
  • Euphoria
  • Miosis
39
Q

Specific side effects of Propoxyphene and Pethidine?

A

Propoxyphene = arrhythmia

Pethidine = neurotoxicity = convulsion/ seizure esp. in kidney failure/ fast liver metabolizer

40
Q

Why is miosis a useful indicator of opioid intake?

A

Persists effect even after lifelong opioid abuse: useful for:

 Unconscious patients

 check for injection marks

 Telling whether the patient takes the drug

41
Q

List side effects from long term opioid use?

A

Acute side effects

Constipation

Dependence: physical

Addiction

Tolerance

42
Q

Define dependence on opioids.

A

Dependence is not addiction

Physical dependence:
= physiological adaptation of body to the presence of an opioid
= development of withdrawal symptoms after chronic use when:

 Opioids are discontinued;
 Dose is reduced abruptly;
 An antagonist (e.g. naloxone) / agonist-antagonist (e.g. pentazocine) is administered

43
Q

Define addiction on drugs?

A

compulsive use of drugs for nonmedical reasons

Characterized by a craving for mood-altering drug effects, not pain relief

44
Q

What dysfunctional behaviors may arise from drug addiction?

A 
 Denial of drug use 
 Lying 
 Forgery of prescriptions 
 Theft of drugs from other patients / family members 
 Selling, buying drugs on the street 
 Using prescribed drugs to get "high"
45
Q

Define tolerance to drugs?

A

physiological state characterized by decreased effects of a drug (e.g. analgesia, nausea or sedation) with chronic administration

> > higher dose to get same effect

i.e. due to reduced downstream events of opioid receptors (expected)

46
Q

Technique used to control opioid administration?

A

Patient controlled analgesia (PCA)

47
Q

Mechanism of PCA in opioid admin?

A

Find desirable plasma conc. range for opioids

  • Increase loading dose until side effects appear to set upper limit
  • Repeated self- admin. within safe zone for Post- op pain relief: sufficient analgesia vs. respiratory depression
48
Q

Pethidine, morphine and methadone. Rank euphoria?

A

pethidine>morphine> methadone

49
Q

T1/2, MoA and indication of Naloxone (Narcan)?

A

pure competitive antagonist (binds on opioid receptor but zero effect

Treats opioid overdose

Half-life ~75 min-1 (shorter T1/2 than most agonist)
Need constant monitoring and admin to ensure safe levels

MBBS II HNNS (57 decks)

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