8 - Pharmacology of Pain Flashcards
What causes central sensitisation
2nd order neurons at the dorsal horn release glutamate and peptides
the GLUT acts on AMPA and NMDA receptors in the SC
Persistent activation of AMPA and NMDA causes altered gene expression and INC in intracellular CA (inc depolarisation) and up-regulation of PGs and COX enzymes
Where do opioid receptors act in the NS
PAG
NRPG
Dorsal horn
Periphery
Factors that influence pain perception
Cognition
Mood
Context
Genetics
Ligands of opiods
POMC - Propriomelanocortin
Proenkephalin
Prodynorphin
Characteristics of Opioids
Co-release
Co-transmission
Relative receptor selectivity
How many kappa receptors are there
3
What type of molecule are opioids
Peptides
What is the action of morphine
Potassium activation
Decrease in calcium conductance
Overall decreased excitability and decreased release of NTS
Examples of opioids
Codeine Tramadol Morphine Oxymorphone Hydrocodone Methadone
Effects of opioids on CNS
Analgesia, respiratory depression, drowsiness, euphoria, nausea
Effects of opioids on CVS
Hypotension
Effects of opioids on GI system
Constipation,
urinary urgency
Opioid with active metabolite M6G
Morphine
Opioid with high solubility and used in cachexia
Heroin
U1 receptor agonist – less respiratory depression
Meptazinol
opiate antagonist with short half life
Naloxone
Paracetamol
reduces the active oxidised form of COX-2
Analgesic, antipyretic but little anti-inflammatory effect
Action of NSAIDs
Inhibition of COX enzymes
Aspirin
COX-1 and COX-2 inhibitor): analgesic, antipyretic, anti-inflammatory
Ibuprofen, diclofenac, ketoprofen
COX-1 and COX-2 inhibition
analgesic and anti-inflammatory effects
Refecoxib
Selective COX-2 inhibitor
Indications of NSAIDS
Rheumatoid arthritis, osteoarthritis, dysmenorrhea, gout, muscle spasm
SE of NSAIDs
Nausea
GI bleeding
Other non-opioid medication
Anticonvulsants
TCAs
Anticonvulsants
Carbamazepine, Sodium valporate - act on Na channels
Pregabalin - Acts on A2d subunit of Ca channels
TCA
Amitriptyline - Inhibit the reuptake of amines and block Na and Ca channels
Examples of local anaesthetics
Lignocaine
Bupivacaine
Prilocaine
MoA of local anaesthetics
Blockade of Na channels
Mode of administration of local anaethetics
surface, infiltration, epidural…
Risk in local anaesthetics
hypotension, respiratory depression, bradycardia
Mode of administration of general anaesthetics
inhalational or intravenous
Mechanism of action of general anaethetics
activation of inhibitory receptors or inhibition of excitatory receptors
Inhalation general anaethetics
Halothane, Xenon, NO, Enflurane, Isoflurane, Desflurane, Sevoflurane
Intravenous general anaesthetics
Propofol, Thiopental, Etomidate, Ketamine, Midazolam
What is the most common facial pain syndrome
Trigeminal neuralgia
Symptoms of trigeminal neuralgia
Sudden, paroxysmal attacks of pain: electric shock-like, sharp, stabbing, commonly unilateral, lasts from a few seconds to a few minutes
Cause of trigeminal neuralgia
Compression, distortion or stretching of the nerve V root fibres by a branch of the anterior or posterior inferior cerebellar artery
Treatment of trigeminal neuralgia
carbamazepine
