Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CPT > L14 - Opiods > Flashcards

L14 - Opiods Flashcards

1
Q

Nociception

A

Non conscious neuronal activity due to trauma or potential trauma to tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Pain

A

Complex awareness of sensation modified by experience, expectation, immediate context and culture involving the somatosensory cortex interpreting pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Pain pathway

A
  1. Tissue damage releases mediators e.g. serotonin, bradykinin and prostaglandins
  2. Nociceptors are stimulated
  3. Substance P, glutamate and bradykinin is released which agonises the local inflammatory response
  4. Afferent nerve is stimulated which projects to the dorsal horn (lamina 1 and 5)
  5. Fibres decussate at the ventral white commissure
  6. Fibres ascend via the 2nd order neurone in the lateral spinothalamic tract
  7. Synapses in the thalamus
  8. Projects to the post central gyrus (primary sensory cortex)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

A fibres

A

Myelinated

Sharp pain transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

C fibres

A

Unmyelinated
Dull ache pain
Requires more stimulation
Slower in transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What modulates pain?

A

Centrally - periaqueductal grey

Peripherally - substantia gelatinosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Substantia gelatinosa

A

Tissue damage inhibits the substantia gelatinosa so pain is felt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Rub wound

A

Rubbing the wound stimulates the substantia gelatinosa which inhibits lamina 1 and 5

Therefore reduced pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Periaqueductal grey

A

The cortex normally inhibits the periaqueductal grey matter

  • when pain is overwhelming, the cortex stimulates the periaqueductal grey matter
  • stimulates the release of endogenous opioids i.e. enkephalins, dynorphins and beta endorphins which act on endogenous opioid receptors
  • inhibits signals to the dorsal horn
  • reduces pain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

MOP receptors

A

Mu GPCR

Location: supraspinal and GI tract

cAMP: decreases

Effect: K+ efflux

Causes:

  • hyperpolarisation
  • decrease in substance P release - less local inflammation and agonisation
  • increases dopamine release

Endogenous opioids:

  • enkephalins
  • Beta - endorphins

Uses:

  • analgesia
  • depression
  • euphoria
  • dependence
  • respiratory sedation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

DOP receptors

A

Delta GPCR

Location : wide distribution

cAMP: decreases

Effect: inhibits influx of Ca2+

Causes:

  • hyperpolarisation
  • decreased release of substance P
  • increases dopamine release (as less GABA released so less inhibition)

Endogenous Opioid:
- enkephalins

Use:
- analgesia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

KOP receptors

A

Kappa GPCR

Location: spinal cord/ brain and periphery

cAMP: decreased

Effects:

  • K+ efflux
  • inhibits Ca2+ influx

Causes:

  • hyperpolarisation
  • decreased substance P
  • increases dopamine release

Endogenous Opioid:
- dynorphins

Uses:

  • Analgesia
  • diuresis
  • dysphoria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

WHO analgesic ladder

A

Simple analgesia: paracetamol, NSAIDs

Weak opioid: codeine - very addictive with many side effects

Strong opioid: morphine and fentanyl
- used in acute severe or malignant pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Other effects of opioids

A

Used in:

  • Cough
  • Diarrhoea - particularly chemotherapy induced
  • Palliation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Morphine

A

Strong agonist of MOP

Absorption:

  • gut absorption can be erratic as motility is slower
  • significant first pass effect - 40% bioavailability

Distribution:

  • lipophilic so enters all tissues
  • passes through placenta - babies can get morphine withdrawal
  • doesn’t pass blood brain barrier

Metabolism:
- glucoronication in liver to active metabolites M3G and M6G

Elimination:
- renal

Action:
Analgesia and euphoria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

M6G and M3G

A

M6G - Analgesic effect

M3G - neuroexcitatory and euphoria

17
Q

Side effects of morphine

A

Respiratory distress - medullary resp centres are less responsive to CO2
Emissions - stimulates the chemoreceptor trigger zone
GI- decreases motility and increases sphincter tone - constipation
Cardiovascular - lowers BP and causes vasodilation - syncope
Miosis - constriction of pupils
Histamine release - caution in asthmatics - itchy and can trigger asthma attack

18
Q

Fentanyl

A

Administration:

  • IV, intrathecal (in CSF space), epidural or nasal
  • 80-100% bioavailability

Distribution

  • highly lipophilic therefore wide distribution
  • highly protein bound
  • passes blood brain barrier

Metabolism
- hepatic CYP3A4

Elimination

  • renal - less than morphine therefore better for renal patients
  • short half life (6mins)

Use:
- pre operative analgesia and anaesthetic

19
Q

Fentanyl compared with morphine

A

100x more potent
Higher affinity for MOP - shifts morphine off

Less side effects of:

  • constipation
  • histamine release
  • sedation
20
Q

Fentanyl side effects

A

Respiratory distress
Vomiting
constipation

21
Q

Codeine

A

Administration: oral or subcutaneous injection

Metabolism:
Codeine is metabolised to morphine via CYP2D6

Elimination:
Glucoronidation of morphine by the liver (second pass) and really excreted

Use:
Analgesia
Cough depressant

22
Q

CYP2D6

A

Inhibited by fluoxetine and other SRRIs

Variably expressed - Caucasians have a higher prevalence of 2 null alleles therefore codeine is not metabolised to morphine so no effect.

23
Q

Codeine potency

A

1/10th of morphine potency

24
Q

Side effects of codeine

A

Constipation - give laxative

Respiratory distress - worse in under 12s

25
Q

Buprenorphine

A

Mixed agonist and antagonist (partial agonist)

Administration:

  • transdermal patch
  • buccal
  • sublingual

Distribution:

  • very lipophilic - highly distributed
  • passes blood brain barrier

Metabolism:

  • hepatic CYP3A4
  • glucoronidation before biliary excretion (good for renal patients)

Elimination:

  • biliary excretion - safe in really impaired
  • long half life

Use:

  • used in moderate to sever pain - chronic pain in elderly
  • opioid addiction treatment
26
Q

Buprenorphine compared to morphine

A

High affinity for MOP - not easily displaced
Longer duration of action
Partial agonist - Lower efficacy
Antagonist at KOP

27
Q

Side effects of buprenorphine

A 
(Less severe)
Respiratory distress 
Low BP 
Nausea 
Dizziness
28
Q

Naloxone

A

Competitive antagonist of opioid

Administration:

  • IV or IM injection
  • not very effective when given orally as low bioavailability (first pass)

Distribution
- lipophilic - rapid wide distribution

Metabolism:
- hepatic glucoronidation

Excretion:

  • renally excreted
  • short half life - given as slow infusion
  • rapid onset and elimination (30-60mins)

Use:
- opioid overdose

29
Q

Nalaxone compared to morphine

A

affinity for mu, then delta then kappa

Higher affinity than morphine but less than buprenorphine

30
Q

Opioid tolerance mechanism

A
  • Phosphorylation and uncoupling

- cAMP production

31
Q

Phosphorylation and uncoupling

A
  1. Repeated exposure of opioid causes intracellular phosphorylation mediated by PKC and Ca2+ dependent proteins within the cell
  2. Arrestin proteins bind to MOP and uncouple the G protein
  3. Opioid doesn’t bind as readily therefore sensitivity decreases and cAMP production doesn’t decrease
32
Q

cAMP production

A
  1. When opioids bind they decrease cAMP
  2. When the opioid is not given, there is a rebound effects where the cell is flooded with cAMP
  3. A higher dose is needed to reduce cAMP to reduce pain
  4. More cAMP causes increased depolarisation
  5. Increases neuronal excitability
  6. Leads to withdrawal symptoms
33
Q

Withdrawal symptoms of opioids

A 
Nausea and vomiting 
Muscles cramps
Abdominal pain 
Constipation and diarrhoea 
Sweating 
Agitated and anxious
34
Q

Overdose

A

Can cause death due to respiratory depression

  • drowsy therefore not breathing as quickly
  • decreased medullary responsiveness to CO2
  • acidosis

Decreases effects of - DOP agonists and serotonin agonists

Hypoxia - pulmonary oedema and vasodilation

35
Q

Special considerations

A
  • drivers - makes drowsy
  • elderly - distribution changes due to change in fat: muscle distribution
  • bedbound
  • asthmatics and respiratory disease - respiratory depression and histamine
  • biliary tract obstruction
  • renal impairments - give fentanyl or codeine
  • ## pregnancy - morphine withdrawals
36
Q

Contraindications

A 
Hepatic failure 
Acute respiratory distress
Comatose
Head injuries 
Raised ICP - can mask symptoms

CPT (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions