pharmacology of pain Flashcards
give weak and strong opioids
weak - codeine and tramadol
strong - morphine, fentanyl, heroin
what is the primary mechanism of action of opioids
depressant effect on cellular activity, has multiple sites in pain pathways where activation of opioid receptor gives decreased perception or increased tolerance to pain
how do opioids have an antitussive effect and what does this mean
anti tussive = suppresses coughs
due to decreased activation of afferent nerves relaying cough stimulus from airways to brain
drug target for opioids
opioid receptor
side effects of opioids
mild nausea and vomiting (increase in chemoreceptor trigger zone) and constipation (opioid receptor in GIT can reduce gut motility)
what happens when u overdose on opioids
respiratory depression (direct and indirect inhibition of respiratory control centre)
co amoxiclav mechanism of action
amoxicilin binds to penicilin binding proteins, preventing transpeptidation (cross linking for bacterial cell wall synthesis)
clavulanate inhibits beta lactamase which degrades beta lactam antibiotics and gives resistance
drug target for co amoxiclav
amoxicilin = penicillin binding proteins
clavulanate = beta lactamase
side effects of co amoxiclav
nausea and diarrhoea
hypersensitivity to penicillin leads to what
rash but can lead to anaphylactic reactions
is amoxicillin for gram positive or negative
both as it is a broad spectrum
lactulose mechanism of action
non absorbable disaccharide, reaches large bowel unchanged, causes water retention via osmosis and an easier to pass stool, can be metabolised by colonic bacteria, colonic metabolism of sugars has additional laxative effect
drug target of lactulose
no drug target
side effects of lactulose
abdominal pain, diarrhoea, flatulence, nausea
how long does lactulose take to work
within 8-12h but make take upto 2 days to improve constipation
when is lactulose prescribed
often prior to starting opioid therapy to improve the very common side effect of constipation
if diagnosed with gastroenteritis how should u be managed
oral rehydration - diarrhoea and vomiting risks dehydration
analgesia
what do u give for mild, mild to moderate and moderate to severe pain
mild - non opioid +/- adjuvant therapy
mild to moderate - weak opioid +/- nonopioid +/- adjuvant therapy
moderate to severe - strong opioid +/- nonopioid +/- adjuvant therapy
what does paracetamol 1g PO QDS PRN mean
to be taken 4 times daily (QDS) when required (PRN) by mouth (PO)
what are the different steps in the pain pathway
stimulus at skin leads to transduction, this is transmitted upto CNS where there is perception in the brain, then modulation goes from brain down to spine (these consist of inhibitory signals down to the spinal cord to inhibit the incoming stimulus, this allows us to function enough to respond to the pain by reducing its signal through neuronal disinhibition)
what is andamide
can be broken down into arachidonic acid by fatty acid amide hydrolase so when NSAIDs and paracetamol inhibit prostaglandin prodction there is a build up arachidonic acid
leads to build up of andamide
it activates descending pain pathways which are the inhibitory ones so andamide gives analgesia
what signs can u see in acute appendicitis
worsening pain over 2h, moved to RLQ, tender in right iliac fossa, guarding and rebound tenderness, high WCC count and CRP
what do u do for acute appendicitis
surgery - open laparoscopy
hydration - would need to be NBM so IV crystalloids
analgesia
antibiotics
why do u give antibiotics in acute appendicitis pre op
obstructed appendix could lead to bacterial overgrowth, plus risk of post-surgical infection
