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4 Clinical Pharmacology and Intro to Prescribing > 16 Opioids > Flashcards

16 Opioids Flashcards

(38 cards)

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1
Q

Differentiate between nociception and pain.

A

Nociception= non concious neural traffic due to trauma or potential trauma to tissue

Pain= complex, unpleasant awarness of sensation modified by experience, expectation, immediate context and culture

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2
Q

How do we feel pain? (explain the pathway)

A
  1. Nociceptors stimulated
    1. Release Substance P and Glutamate
  2. Afferent nerve stimulated
    1. A delta fibres= sharp pain
    2. C fibres= dull pain
  3. Fibres decussate then ascend
  4. Synapse in thalamus
  5. Project to post central gyrus
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3
Q

We can modulate pain peripherally and centrally. Where can the modulators be found?

A

Peripherally: substantia gelatinosa

Centrally: peri aqueductal grey

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4
Q

How do we modulate pain peripherally?

A

Substantia gelatinosa

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5
Q

How do we modulate pain centrally?

A
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6
Q

Name 3 endogenous opioids.

A

Enkephalins

Dynorphins

B-endorphins

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7
Q

What receptors do the endogenous opioids act on? (3) Where are each of these receptor types found and what actions do they have?

A
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8
Q

Outline the WHO analgesic ladder:

A
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9
Q

What drug types might be give to treat neuropathic pain?

A

Anticonvulsants

Tricyclics

Serotonin/Noradrenaline reuptake inhibitors

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10
Q

In general, how to opioids work?

A

Exploit endogenous opioid receptors

Main effect= via μ- receptors

Aim to modulate pain

(Also indicated in: - cough, diarrhoea, palliation)

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11
Q

There are many different drugs in the opioid class. Give an example of a:

Strong agonist

Moderate agonist

Mixed agonist/antagonist

Antagonist

A

Strong agonist

  • Morphine
  • Fentanyl

Moderate agonist

  • Codeine

Mixed agonist/antagonist

  • Buprenorphine

Antagonist

  • Naloxone
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12
Q

How is morphine administered? Why does it sometimes need to be administered IV rather than orally?

A

Orally

IV

Intramuscular

Sub cut

PR

Gut absorption erratic and only has 40% oral availability due to first pass metabolism

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13
Q

Can morphine enter the foetal tissue?

A

Yes- can enter all tissues including foetal BUT not very good at crossing blood brain barrier compared to other opioids

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14
Q

Where is morphine metabolised and excreted?

A

Metabolised: liver

Excreted: renally

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15
Q

What action does morphine have? How does it work?

A

Strong affinity for μ-receptors, minimal for K and δ.

Complete activation of μ

Actions:

  • Analgesia
  • Euphoria
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16
Q

Give 6 side effects of morphine:

17
Q

How is fentanyl abdministered? What’s its bioavailability like?

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A

Fentanyl

Administered:

  • IV
  • Epidural
  • Intrathecal (into CSF)
  • Nasal

Bioavailability:

  • 80-100%
18
Q

How well does Fentanyl cross the blood brain barrier? How is fentanyl metabolised and excreted?

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A

Well- highly lipohilic, highly protein bound

Metabolism: Hepatic - CYP3A4

Elimination: Renally excreted (half-life= 6 mins)

19
Q

What actions does fentanyl have?

Study These Flashcards
A

Actions of fentanyl:

  • Analgesia
  • Anaesthetic
20
Q

How does fentanyl compare to morphine (in terms of affinity for μ-receptors and side effects)

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A

Affinity:

Higher affinity for μ-receptors

Side effects:

Less:

  • Histamine release
  • Sedation
  • Constipation
21
Q

What side effects might a patient get from taking fentanyl? (3)

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A
  1. Respiratory depression
  2. Constipation
  3. Vomiting
22
Q

How is codeine administered?

Study These Flashcards
A
  • PO (Per Os)
  • Sub cutaneous
23
Q

How does codeine work? Why might its effects be different within the population? How is it eliminated?

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A

Codeine–> Morphine via CYP2D6

Varying CYP2D6 in population

CYP2D6 inhibited by Fluoxetine (SSRI)

Eliminated: same way as morphine

Glucoronidation of morphine and renal excretion

24
Q

What actions does codeine have? How does it differ from morphine in terms of potency?

Study These Flashcards
A

Codeine= 1/10th potency compared to morphine

Actions:

  • Mild-moderate analgesia
  • Cough depressant
25
What are the 2 main side effects of codeine?
1. Constipation (give patient laxatives- esp elderly) 2. Respiratory depression= worse in children
26
How is Buprenorphine administered?
Transdermal (patch), buccal, sublingual = very lipophilic
27
How is Buprenorphine metabolised and excreted?
Metabolised: Hepatic- CYP3A4 Glucoronidation Elimination: Biliary \> Renal SAFE in renal impairment half life= 37 hrs
28
What actions does Buprenorphine have and how does it exert its effects?
Buprenorphine Actions: * Moderate-severe pain * Opioid addiction treatment Mechanism: * High affinity for μ-receptor, antagonist at K receptors * Lower E(max) than morphine (as= partial agonist) * Long duration of action
29
Give some of the side effects of Buprenorphine.
* Respiratory depression * Low BP * Nausea * Dizziness
30
How can Naloxone be administered? What's its bioavailability like?
Administration: * IV * IM * Intransal * PO --\> Needs to be given as **slow infusion** allow heroin/morphine to metabolise Bioavailability: * = very low- extensive FIRST PASS EFFECT * --\> rapid onset of action * (duration of action= 30-60mins)
31
How is naloxone metabolised and excreted?
Hepatic--\> naloxone-3-glucuronide Renally excreted
32
What is naloxone used for?
Used for opioid overdose (reversal agent) Will dislodge anything at μ receptors (except **buprenorphine**)
33
What are the 2 main mechanisms that cause opioid tolerance?
1. Phosphorylation and uncoupling 1. Repeated exposure 2. Intracellular phosphorylation 1. Reduced sensitivity of opioid receptor or 2. Arrestin proteins bind to receptor instead of g-protein 2. cAMP production 1. Opioid given= reduces intracellular cAMP 2. Opioid withdrawn- cell flooded with cAMP 3. 'Rebound effect' 1. Explains withdrawal symptoms- increase neuronal excitability
34
Who would you need to make special considerations for when prescribing opioids? (8)
35
Give some contraindications for opioids.
36
What does PRN mean? (with relation to prescribing)
= pro re nata = **AS NEEDED**
37
Opioids are strictly controlled drugs (under misuse of drugs legislation). What information should you make sure to record if prescribing opioids to a patient?
38
With opioids- start low and titrate up. Useful info - most common prescriptions:

4 Clinical Pharmacology and Intro to Prescribing (27 decks)

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