intro to opioids Flashcards
what is opium extracted from
papaver somniferum
products derived from opium
white milky latex containing alkaloids
extraction focused on obtaining morphine
heroin and codeine
what is thebaine synthesised into
oxycodone
hydrocodone
3 main types of opioid receptor and what for
mu for morphine
kappa for ketcyclazocine
delta for deferens
function of opioid peptide receptors
G-protein coupled - opens K+ channels and closes Ca+ channels
main funcrtion of Mu receptors
analgesia and euphoria
constipation and respiraotry depression
main functtion of kappa receptors
analgesic at periphery
dysphoria and hallucinations
main function of delta receptors
analgesia at spine
CNS effects of morphien
analgesia
euphoria
sedation
pupillary constriction - stimulation of oculomotor nucleus brainstem
GI effects of morphine
nausea and vomiting - chemoreceptord trigger zone in medulla
constipation - reduced motility and muscle tightening
respiratory effects of morphine
depression - inhibits respiratory centres in brainstem
suppress cough reflex
tolerance of morhine with recurrent uses
desensitisation of mu receptors
increasing doses needed to acheive sufficient analgesia
3 pharmacokinetic considerations when prescribing morphine
most morphine derivatives have short half-life so must be given several times a day
metabolised in liver, then excreted in urine
sustained release tablets available and synthetic opioid skin patches to reduce pill burden
opioid receptor antagonists
naloxone
reverses opioid actions of Mu receptor
given via Iv or subcut in acute opioid toxicity
other antagonists are methylnaltrexone, naloxegol, naltrexone
metabolism of codeine
3-methoxymorphine demethylated by liver CYP2D6 to become morphine
