pharmacology of painkillers

Question 1

mechanism of action of paracetamol

Answer 1

still not fully clear

peripheral sites - may inhibit an enzyme involved in the conversion of arachidonic acid to prostaglandins.
Ability of paracetamol to inhibit peroxidase can be blocked if excessive levels of peroxide build up (seen in inflammation)

Question 2

action of paracetamol on serotonergic pathways

Answer 2

activation of descending serotonergic pathway possibly via 5ht3 receptor activation

Question 3

effect of paracetamol on cannabinoid receptors

Answer 3

it inhibits reuptake of endogenous endocannabinoids - increases activation of endo cannabinoid receptors - contributing to activation of descending pathways

Question 4

drug target of paracetamol

Answer 4

unclear

h5t3 receptor/ endocannabinoid reuptake protein/peroxidase

Question 5

main side effects of paracetamol

Answer 5

relatively safe
overdose - liver damage and less frequently renal damage
nausea and vomiting = early features of poisoning

Question 6

example of strong and weak opioids

Answer 6

weak - codeine, tramadol

strong - morphine, fentanyl, heroin

Question 7

mechanism of action of opioids

Answer 7

overarching - depressant effect on cellular activity
there are multiple sites within pain pathway where activation of opioid receptor. leads to decreased perception/increased tolerance to pain
antitussive effect due to decreased activation of afferent nerves relaying cough stimulus from airways to brain

Question 8

target of opioids

Answer 8

opioid receptor

Question 9

side effects of opioids

Answer 9

mild - nausea and vomiting (increase activity in chemoreceptor trigger zone)
constipation - can reduce gut motility

Question 10

mechanism of action of co amoxiclav

Answer 10

binds to bacterial penicillin binding proteins
- prevents transpeptidation
clavulanate - inhibitor of beta lactamase - can usually degrade beta lactam

Question 11

side effects of amoxicillin

Answer 11

well tolerated
- nausea and diarrhoea

• hypersensitivity to penicillins is relatively common
• usually associated with rash but can lead to anaphylactic rections

Question 12

mechanism of action of lactulose

Answer 12

non absorbable disacharide
reaches nowel unchanged
causes water retention via osmosis and easier to pass stool. can also be metabolised by colonic bacteria

Question 13

side effects of lactulose

Answer 13

abdo pain
diarrhoea
flatulence
nausea

Question 14

how long does lactulose take to begin working

Answer 14

8-12 hrs

may take upto 2 days to improve constipation