Pain/MSK Drugs Flashcards
class and mechanism of diclofenac
NSAID
inhibits COX1 & 2, preventing prostaglandin synthesis
side effects of diclofenac?
GI disturbance/bleeds
renal failure
associated with significantly increased vascular and coronary risk
not used that much anymore
How does codeine work?
Metabolised in liver to form small amounts of morphine/ dihydromorphine
activate opioid mu receptors
How is tramadol similar to codeine
is a synthetic analogue of codeine
also acts as a serotonin and noradrenaline reuptake inhibitor
contraindications of codeine
significant respiratory disease
renal/hepatic impairment
tramadol lowers seizure threshold so avoid in epilepsy
can codeine be given IV?
no never
this can cause a severe histamine mediated but non-allergic reaction
what other effects does morphine have other than on mu receptors
blunts the response to hypercapnoea and hypoxia, reducing resp drive
reduces sympathetic effects
Can you give morphine for biliary colic pain?
No
may cause spasm of sphincter of Oddi, worsening pain
how does paracetamol work?
weak inhibitor of COX
has specificity for COX2 over COX1
describe the mechanism of paracetamol overdose
metabolised to form NAPQI, which is conjugated with glutathione to be removed
pathway becomes saturated, NAPQI causes hepatocellular necrosis
treated with acetylcysteine, glutathione precursor
what is the maximum daily dosage of paracetamol allowed
0.5-1g every 4-6 hours
max 4g daily
mechanism of allopurinol?
xanthine oxidase inhibitor
prevents production of uric acid
why shouldn’t you start allopurinol during an attack of gout
initially makes it worse
interactions of allopurinol
azathioprine and marcaptoprine require xanthine oxidase for metabolism
increases risk of toxicity
