Opioids Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

How is pain formed?

A

1) stimulation of nociceptors
2) release of substance P and glutamate
3) stimulation of afferent nerves
4) decussation of fibres
5) action potential ascends
6) synapse in thalamus
7) project to primary sensory cortex

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

What are the pain modulators?

A

Peripherally:
Substantia gelatinosa

Centrally:
Peri aqueductal grey

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

What are examples of endogenous opioids?

A

Enkephalins
Dynorphins
B-endorphins

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

What receptors do opioids act on?

A

μ - enkephalins, B-endorphins

δ - enkephalins

κ - dynorphins

All GPCRs

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

What is the WHO analgesic ladder?

A

Simple analgesia - paracetamol, NSAIDs
Weak opioid - codeine
Strong opioid - morphine, fentanyl

Typically used for chronic pain
If acute pain, can go straight to strong opiate

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

What is the general principles of opioid use?

A

Exploit natural opioid receptors - agonist or antagonism
Mainly act via μ receptors

Aim to modulate pain
Also indicated in cough, diarrhoea and palliation

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

Describe pharmacokinetics of morphine

A

Absorption:
PO, IV, IM, SC, PR
Erratic gut absorption
Significant first pass

Distribution:
Rapidly enters all tissues, inc foetal

Metabolism:
Morphine + glucuronic acid => M6G + M3G

Elimination:
Renal

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

What are the actions of morphine?

A

Strong agonist
Bind to μ receptors

Causes analgesia and euphoria

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

What are some side effects of morphine?

A

Respiratory depression - medullary resp centre made less responsive to CO2
Emesis - stimulates CTZ
Decreased GI motility => constipation
Miosis
Mast cell degranulation => histamine release - be careful w/ asthmatics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe pharmacokinetics of fentanyl

A

Absorption:
IV, epidural, intrathecal, nasal
80-100% bioavailability

Distribution:
Highly lipophilic and protein bound
High level of CNS membrane

Metabolism:
CYP 3A4

Elimination:
Half life 6 mins
Renally excreted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the actions of fentanyl?

A

Strong agonist

Analgesia
Anaesthetic

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

What are the side effects of fentanyl?

A

Respiratory depression
Constipation
Vomiting

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

Describe the pharmacokinetics of codeine

A

Administration:
PO, SC

Metabolism:
Codeine => morphine via CYP 2D6

Elimination:
Glucoronidation of morphine
Renal excretion

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

What are the actions of codeine?

A

Moderate antagonist

Mild - moderate analgesia
Cough depressant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the side effects of codeine?

A

Constipation

Respiratory distress

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

Describe the pharmacokinetics of buprenorphine

A

Administration:
Transdermal, buccal, sublingual

Distribution:
V lipophilic

Metabolism:
Hepatic via CYP 3A4

Elimination:
Biliary excretion
Therefore safe in renal impairment
Half life 37 hrs

17
Q

What are the actions of buprenorphine?

A

Mixed agonist-antagonist

V high affinity for μ receptor, low Kd

Used for moderate to severe pain
Also used for addiction treatment

18
Q

What are some side effects of buprenorphine?

A

Respiratory depression
Low BP
Nausea
Dizziness

19
Q

Describe the pharmacokinetics of naloxone

A

Absorption:
IV, IM, intranasal, PO
V low bioavailability - extensive first pass metabolism
Rapid onset of action

Distribution:
V lipophilic

Metabolism:
Hepatic => naloxone-3-glucoronide

Elimination:
Renal

20
Q

What are the actions of naloxone?

A

Antagonist

Greater affinity than morphine and fentanyl

Competitive antagonism of opioid

21
Q

What are the side effects of naloxone?

A

Short half life

Tf give slow infusion - pt has time to metabolise morphine

22
Q

How does opioid tolerance occur?

A

When giving synthetic opioids, the number of opioid receptors increases

Requires a higher dose of opioid required to get enough binding for a cell response

23
Q

How does opioid withdrawal occur?

A

Suddenly taking away a synthetic opioid means that there is a lower percentage of binding to receptors

Therefore don’t get a cell response

24
Q

What are the actions of methadone?

A

Used to avoid withdrawal Sx
Binds to opioid receptors
Slowly decrease dose to decrease number of receptors
Removes some side effects

25
Q

What are some special considerations for opioids?

A
Manual labourers/drivers
Elderly 
Bedbound
Asthmatics
Biliary tract obstruction 
Respiratory disease 
Renal impairment 
Pregnancy
26
Q

What are some contraindications for opioids?

A
Hepatic Failure 
Acute respiratory distress
Comatose 
Head injuries 
Raised ICP
27
Q

How are opioids prescribed in palliative care?

A

Buprenorphine, diamorphine, fentanyl, morphine and oxycodone all prescribed

Tend to ignore special considerations eg renal impairment

Indications: pain, shortness of breath

Also need to manage side effects like nausea and constipation

28
Q

Why are some opioids controlled drugs?

A

To prevent:
Misuse
Illegal obtainment
Any harm being caused