Pain and Analgesia Flashcards Preview

PM3B: Autumn > Pain and Analgesia > Flashcards

Flashcards in Pain and Analgesia Deck (48):
1

What is the best definition of pain

An unpleasant sensory or emotional experience associated with actual or potential tissue damage, or described in terms of such damage

2

What are the two classes of pain

Nociceptive pain

Neuropathic pain

3

Describe how Nociceptive pain works and give examples of it

Peripheral visceral or somatic pain
Directe action of pain sensing receptors in response to noxious stimuli that alerts organic of impending tissue damage

Examples:
Inflammation
Fractures
Burns
Bumps and bruises

4

Describe how Neuropathic pain works and give examples of it

Pain produced by damage to dysfunction of nerves in peripheral or central nervous system

Examples:
Nerve
Trauma
Peripheral neuropathy
Phantom limb pain

5

What are the three processes of nociceptive pain

1. Detection of pain in the periphery

2. Transmission of pain signals from periphery to spinal cord- mainly by C fibres and Adelta fibres

3. Reception of signals by higher central brain centers- afferent activity generates pain sensation that initates response

6

What is the function of A beta fibres

Touch and pressure (mechanoreceptors)

Target of TENS and acupuncture

7

What is the function of A delta fibres

Sharp pain (NOCICEPTORS)

Touch (Mechanoreceptors)

8

What is the function of C fibres

Dull and burning pain (NOCICEPTORS)

Touch (Mechanoreceptors)

Temperature (Thermoceptors)

9

What is the gate control pain theory

Formed of transmission neurones which supply the thalamus area of brain with sensory information

The neurones are affected by:
Small inhibitory neurones
Nociceptors (C and A delta fibres)
Mechanoreceptor (A Beta fibre) input

10

Describe the gate control pain theory (4 steps)

1. Small inhibitory neurones (substantial gelantinosa SG interneurones) that inhibit and close the gate to reduce pain

2. Activation of C and A-delta fibres open the gate and increase pain by direct excitation of the gate and inhibition of SG interneurones

3. Activation of A beta fibres to close the gate- excitation of SG interneurones

4. Descending inhibitory pathways from the CNS close the gate by:
Inhibition of the gate and direct activation of SG interneurones

11

What are the six inflammatory mediators of peripheral pain

1. Bradykinin

2. Substance P

3. Adenosine Triphosphate (ATP)

4. Protons (H+)

5. Endogenous activators of TRPV1

6. Prostanoids

12

Describe how bradykinin plays a part as an inflammatory mediator of peripheral pain

Made from vascular precursors and activates:

Beta 2 receptors: Nociceptive neurones
Beta 1 receptors: Metabolite unregulated via inflammation

13

Describe how Substance P plays a part as an inflammatory mediator of peripheral pain

Activates NKA (neurokinin) receptors in nociceptive pain

- Enhances NMDA action (hypersensitivity)

- CGRP peptide is co-released

14

Describe how Adenosine Triphosphate plays a part as an inflammatory mediator of peripheral pain

Activates P2X3 receptors

15

Describe how Protons (H+) plays a part as an inflammatory mediator of peripheral pain

Activates acid sensing ion channels (ASICS)

16

Describe how Endogenous activators of TPV1 vanillin receptors plays a part as an inflammatory mediator of peripheral pain

Heat
Target of capsaicin (API in chilli)

It is unregulated by BK and nerve growth factor

17

Describe how PROSTANOIDS plays a part as an inflammatory mediator of peripheral pain

Formed of prostaglandins and thromboxane

PGE2 and PGF2 are released in inflammation- greatly increased responses to bradykinin and 5-HT

18

Describe how GLUTAMATE plays a part as an inflammatory mediator of peripheral pain

Excitatory amino acid that acts at AMPA to mediate acute pain (fast response, baseline set)

NMDA receptor has delayed response

19

What are the two types of neuropathic pain and explain them

Sodium channel clustering- redistribution of sodium channels to areas of nerve damage can set up ectopic (out of place) firing

Sympathetic NS mediated pain- up regulation of alpha adrenoceptor means that noradrenaline release causes pain

20

What are the main drugs for nociceptive and neuropathic pain

Nociceptive pain:
Non opioid: paracetamol, aspirin, NSAIDS
OPIOID analgesics

Neuropathic pain:
Anti-deppresants
Anti-convulsants
Other CNS related drugs

21

What is the mechanism of action of aspirin and its role

Blocks cycloxygenase enzymes
COX-1 (constitutive form)
COX-2 (induced at damage sites) isoforms

Role:
Anti platelet effects (TXA2 effect)
Anti-pyretic (fever reducer)

22

Give examples of non selective NSAIDS

Indoles:
DICLOFENAC and Indomethacin

Propionic acid derivatives:
Ibuprofen
Naproxen
Ketoprofen

23

Give examples of COX-2 selective NSAIDS that were withdrawn

Rofecoxib and Valdecoxib- cardiovascular side effects

24

Give examples of COX-2 selective NSAIDS and their uses

Celecoxib and Etoricoxib
Licensed for Rheumatoid arthritis, osteoarthritis pain and gout

25

What is Nefopam

A non opioid drug that is used for persistent pain when NSAIDS are ineffective

26

What is the mechanism of action of paracetamol

TRPA1 mediates spinal antinociception and this is induced by acetaminophen

27

What does co-dydramol consist of

Paracetamol wit dihydrocodeine tartate

28

What is the main endogenous agonist for mu, delta and kappa receptors in opioid receptor G alpha i/o?

Beta endorphins

29

What is the therapeutic agonist for Mu receptors and its clinical uses

Morphine
Codeine
Fentanyl
Pethidine

All forms of nociceptive pain: cancer, pre/post operative pain

30

What is the therapeutic agonist for kappa receptors

Pentazocine

31

How do you affect spinal action with opioid action

Activation of presynaptic receptors with more Mu than Delta to reduce transmitter release

32

How do you affect Supra-spinal action

Opioid action at mu (delta and kappa) receptors to enhance descending inhibitory pathway in brain stem/mid brain

Involves noradrenaline and 5-HT release by blocking GABA inhibition

33

Describe the use of morphine as a partial agonist of Mu: role, metabolism, dose, route

Reduces affective component pain

Metabolised to morphine-6-glucuronide

Dose: titrated to the amount depending on pain relief

Commonly given via:
IV or oral morphine sulfate (MST)

34

Describe Fentanyl, potency, duration and form

Very potent
Short duration
Often used as a transdermal patch

35

Describe where Pethidine is normally used

Used during labour
Lack of effect of uterine contraction

36

Describe the use of oxycodone

Control of pain in palliative care

37

Describe the use of codeine and dihydrocodeine and its side effects

Low efficacy, orally effective

Not too addictive, widely used for mild pain (back, head, toothache)

Side effects:
CONSTIPATION with long term use
Nausea and Vomiting

38

Describe Diamorphine its pharmacodynamic properties and use

Heroin metabolised to morphine

High lipid solubility means higher efficacy and rapid action

Used in weak patients in palliative care

39

Describe Tramadol and its role

Weak Opioid Analgesic

Inhibitor of noradrenaline uptake and transport system

40

What are the side effects of opioid analgesics and explain how they occur (5)

Respiratory Depression:
Reduction of sensitivity of respiratory centre

Euphoria:
Acts on reward pathway to increase dopamine release
(example: kappa agonist Pentazocine)

Cough suppression (anti-tussive)

Nausea- activation of chemoreceptor trigger zone that activates vomiting centre
(antiemetics co prescribed)

Constipation- maintained contraction of smooth muscle

41

What is the treatment option of respiratory depression

NALOXONE

42

What are the five drugs used to treat neuropathic pain

1. Anti-epileptic drugs

2. Tricyclic (antidepressants)

3. Ketamine

4. Lidocaine or bupivacaine

5. Ziconotide

6. Cannabinoid agonists

43

Give examples of the anti-epilpetic drugs used in neuropathic pain and what they do

1. Carbmazepine and Phenytoin (Na channel blocker)

2. Gabapentin and pregabalin (calcium channel effect)

44

Give examples of Tricyclic anti-depressant drugs used in neuropathic pain and what they do

Duloxetine- selective serotonin and norepinephrine reuptake inhibitor

Imipramine/Amitriptyline

45

What does ketamine do in neuropathic pain

Analgesic block of NMDA receptor

46

What does lidocaine or bupivacaine do in neuropathic pain

Local anaesthetics that block Na Channel (nerve block) when injected close to sensory nerve

47

What does Ziconotide do in neuropathic pain

Acts as a calcium channel blocker and injected intrathecally to spine

48

Give an example of a cannabinoid agonist and what its used to treat

Used to treat pain in multiple sclerosis patients

SATIVEX- mixture of THC and CBD