Flashcards in Analgesia Deck (47)
Loading flashcards...
1
What are the modes of action of analgesics?
Act at side of injury to decrease nociceptor sensitization
Suppress nerve conduction by blocking/ inactivating voltage-activated sodium channels
Suppress synaptic transmission of nociceptive signals in the dorsal horn of the spinal cord
Activate or potentiate descending inhibitory controls
Targeting ion channels upregulated in nerve damage
2
Examples of strong opioids
Morphine
Oxycodone
Hydromorphone
Heroin
Fentanyl
3
Examples of weak opioids
Codeine
Tramadol
Dextropropoxyphene
4
Examples of NSAIDs
Aspirin
Diclofenac
Ibuprofen
Indomethacin
Naproxen
5
What are endogenous peptides?
Endorphine which act upon opioid receptors
6
What mediates the supraspinal antinociception pathway?
Descending pathways from the brainstem
7
Which areas of the brain are involved in pain perception?
Cortex
Amygdala
Thalamus
Hypothalamus
8
What are important brainstem regions in the regulation of pain?
Periaqueductal grey area of midbrain around the 4th ventricle
Locus ceruleus of the pons
Nucleus raphe magnus of the medulla
9
Where will activated PAG neurones project?
Nucleus Raphe Magnus (NRM) to excite 5-HT and enkephalinergic neurones which project to the dorsal horn resulting in suppression of nociceptive transmission
10
Which neurotransmitter will the locus coeruleus utilise in regulation of pain?
Noradrenergic neurones which project to the dorsal horn
11
What are the different types of opioid receptors?
Mu
Delta
Kappa
12
What is the function of Mu?
Responsible for the majority of analgesic action of opioids but also the major adverse side effects
13
What is the function of delta?
Contributes to analgesia but also can be a proconvulsanat
14
What is the function of kappa?
Contributes to analgesia at the spinal and peripheral level and activation assoc with sedation, dysphoria and hallucinations
15
What is the major resp effect of opioids and what is the mechanism?
Apnoea
Blunting of medullary resp centre to CO2 involving Mu and delta receptors
16
What is the major CV effect of opioids and what is the mechanism?
Orthostatic hypertension
Reduced sympathetic tone and bradycardia via actions on medulla
Histamine evoked vasodilation
Morphine can cause mast degranulation which can trigger bronchospasm in asthmatics
17
What is the major GI effects of opioids and what are the modes of action?
N+V, constipation, increased intrabiliary pressure
Actions on CTZ
Increased smooth muscle tone, decreased motility via enteric neurones
Involves Mu and Delta receptors
18
What are the major CNS effects of opioids and what are the modes of action?
Confusion, eurphora, dysphoria, hallucinations, dizziness, myoclonus and hyperalgesia
Occurs to different degrees dependent upon the specific opioid drug and receptor subtypes activated
19
How is morphine metabolised and where?
Liver
Glucuronidation at the 3 and 6 hydroxyl positions
20
What is the impact of glucuronidation at the 3 and 6 positions of morphine?
3 - inactive drug
6 - active analgesic that is excreted renally
21
What is the difference between morphine and diamorphine?
Diamorphine is more lipophilic than morphine
Rapid onset of action (enters CNS)
22
How is codeine metabolised and where?
Hepatic metabolism by demethylation to morphine by cytochrome p450
23
What are common side effects of codeine?
Anti-diarrhoeal
Antitussive
24
What are the semi-synthetic derivatives of codeine?
Oxycodone
Hydrocodone
25
Is fentanyl more or less potent than morphine?
75-100x more potent
26
When is fentanyl commonly given?
IV to provide analgesia in maintenance anaesthesia
27
When is pethidine used?
Acute pain, particularly labour
28
Which drugs can pethidine not be used in conjunction with?
MAO inhibitors as will cause excitement, convulsions and hyperthermia
29
What is the mode of action of tramadol?
Weak Mu receptor agonist
Analgesic action by potentiation of descending serotonergic and adrenergic systems
30
