Pharmacology (Analgesics)

Question 1

ways analgesics can reduce nociception and pain

Answer 1

• decrease nociceptor sensitisation by blocking prostaglandins (NSAIDs)
• suppressing nerve conduction at Na+ channels (lidocaine)
• suppressing synaptic transmission in dorsal horn (opioids)
• activating descending inhibition
• targeting ion channels upregulated

Question 2

analgesic rungs

Answer 2

3/ strong opioid
2/ weak opioid
1/ NSAIDs or paracetamol

Question 3

examples of strong opioids

Answer 3

morphine
heroin
fentanyl
oxycodone
hydromorphone

Question 4

examples of weak opioids

Answer 4

codeine
tramadol
dextropropoxyphene

Question 5

important brainstem regions in pain

Answer 5

periaqueductal grey (midbrain)
locus coeruleus (pons)
nucelus raphe magnus (medulla)

Question 6

what does excitation of PAG cause?

Answer 6

profound analgesia

Question 7

what does NRM cause when activated by PAG?

Answer 7

suppression of nociceptive transmission

Question 8

what does the LC do?

Answer 8

projects to dorsal horn and are excited inhibiting nociceptive transmission

Question 9

what receptor do opioids act on?

Answer 9

GPCR

Question 10

what do opioids do when they bind to GPCR?

Answer 10

inhibit Ca2+ channels (suppressing neurotransmission of nociception) and open K+ (suppress excitation post-synaptically)

Question 11

adverse of opioids

Answer 11

addictive potential
apnoea
orthostatic hypotension
action on CTZ causing N&V
confusion, euphoria, hallucinations

Question 12

how do opioids cause apnoea?

Answer 12

blunts medulla respiratory centre to CO2 causing hypercapnia responses

Question 13

how do opioids cause orthostatic hypotension?

Answer 13

reduce sympathetic tone and bradycardia with mast cell degranulation

Question 14

what do opioid agonists act on?

Answer 14

u-opioid receptors

Question 15

opioid agonists

Answer 15

morphine
diamorphine
codeine
fentanyl
pethidine
buprenorphine
tramadol
methadone

Question 16

what organ metabolises morphine?

Answer 16

liver

Question 17

what organ excretes morphine?

Answer 17

kidney

Question 18

what is diamorphine?

Answer 18

a more lipophilic version of morphine so ha rapid onset

Question 19

additional properties of codeine?

Answer 19

anti-diarrhoeal

antitussive

Question 20

higher potency derivatives of codeine

Answer 20

oxycodone

hydrocodone

Question 21

when is pethidine used?

Answer 21

acute pain, particularly labour

Question 22

what is buprenorphine used in?

Answer 22

chronic pain with patient-controlled injections

Question 23

when should you avoid tramadol?

Answer 23

epilepsy

Question 24

what can methadone be used in?

Answer 24

withdrawal from strong opioids such as heroin

Question 25

opioid antagonists

Answer 25

naloxone
naltrexone
alvimopan and methylnaltrexone

Question 26

when is naloxone used?

Answer 26

reverse opioid toxicity associated with overdose

can trigger acute withdrawal episode

may be given to new-borns with opioid toxicity as a result of administration of pethidine during labour

Question 27

properties of NSAIDs

Answer 27

analgesic
antipyretic
anti-inflammatory

Question 28

action of NSAIDs

Answer 28

inhibit prostaglandins COX1 and COX2
suppress sensitisation of nociceptors by prostaglandins
decrease recruitment of leucocytes
suppression in dorsal horn

Question 29

adverse of NSAIDs

Answer 29

GI damage

Question 30

conditions with neuropathic pain

Answer 30

trigeminal neuralgia
diabetic neuropathy
post-hepatic neuralgia
phantom limb pain

Question 31

management options for neuropathic pain

Answer 31

gabapentin and pregabalin
amitriptyline
carbamazepine

Question 32

action of gabapentin and pregabalin

Answer 32

reduce expression of Ca2+ channels which causes a decrease in neurotransmitters (glutamate and substance P)

Question 33

what neuropathic pain condition is gabapentin used in?

Answer 33

migraine prophylaxis

Question 34

what neuropathic pain condition is pregabalin used in?

Answer 34

painful diabetic neuropathy

Question 35

action of amitriptyline

Answer 35

act centrally by decreasing reuptake of NA

Question 36

action of carbamazepine

Answer 36

block Na+ channels

Question 37

what neuropathic pain condition is carbamazepine used in?

Answer 37

trigeminal neuralgia