Opioids Flashcards
What do nociceptors release when stimulated?
Substance P and glutamate
Which substance modulates pain in the peripheries?
Substantia Gelatinosa
Which substance modulates pain centrally?
Peri aqueductal grey (around mickeys mouth)
What is the WHO analgesic ladder?
Simple analgesic, weak opioid, strong opioid
What receptor do opioids most commonly act on?
mu
What is the distribution of morphine?
enters all tissue including foetal, doesn’t cross BBB
How is morphine eliminated?
renally
What are the side effects of morphine?
respiratory depression, emesis, decreased gut motility, histamine release (caution in asthmatics)
What is the distribution of Fentanyl?
Highly lipophilic and highly protein bound, high level of CNS crossing
Fentanyl vs morphine
Fentanyl is 100x more potent and has a higher affinity for the mu receptor, also used in pre-op for sedation effects
How is codeine metabolised in the body?
Converted to morphine by CYP2D6, which has variable expression
What is buprenorphine used for?
Pateints with kidney problems as it is eliminated by the billiary system, and opiod addiction treatment
What is naloxone used for?
Treat opioid overdose (slow infusion)
What causes reduced opioid sensitivity?
G-protein can uncouple from mu receptor or arrestin can bind to mu receptor, decreasing CAMP in the cell
How does withdrawal occur?
Extended opioid use can cause reduced sensitivity and reduced CAMP in cells, When the opioid is removed lots of CAMP is produced causing neuronal excitability and withdrawal symptoms
