Analgesics

Question 1

Describe the WHO pain ladder.

Answer 1

1 –> 3
1 = paracetamol ± NSAIDs
2 = weak opioids
3 = strong opioid

Combinations of 1+2 or 1+3 for moderate/severe pain

Question 2

Analgesic that suppresses nerve conduction by blocking voltage activated Na channel?

Answer 2

local anaesthetics e.g. lidocaine

Question 3

Analgesic that acts at site of injury to decrease nociceptor sensitisation in inflammation?

Answer 3

NSAIDs block synthesis of prostaglandins

Question 4

Analgesics that target ion channels unregulated in nerve damage?

Answer 4

many anti epileptics e.g. GABA pentinoids

Question 5

Examples of weak opioids

Answer 5

codeine
tramadol
dextropropoxyphene

Question 6

Examples of strong opioids

Answer 6

morphine
oxycodone
hydromorphone
heroin
fentanyl

Question 7

Which efferent pathway from the midbrain is serotonergic?

Answer 7

periaqueductal grey matter

synapses in nucleus raphe magnus which continues serotonergic projection

Question 8

Which efferent pathway from the pons is a noradreneric projection?

Answer 8

locus ceruleus

Question 9

Areas of brain involved in pain perception excite ??? by electrical stimulation to produce profound analgesia.

Answer 9

PAG - periaqueductal grey

Question 10

Where in the spinal cord does nociceptive transmission get suppressed?

Answer 10

dorsal horn

Question 11

What adverse effect do opioids have on the respiratory system?

Answer 11

Apnoea - they blunt the medullary respiratory centre to CO2

= hypercapnia response

Question 12

Why should morphine not be used in asthmatics?

Answer 12

causes mast cell degranulation which can trigger bronchospasm

Question 13

An opioid antagonist produces analgesia mainly through prolonged activation of m-opioid receptors.
T/F?

Answer 13

False

opioid agonist prolongs activation of m-opioid receptors

Question 14

Acute severe pain and chronic pain = which opioid m receptor agonist?

Answer 14

morphine
IV in acute
oral in chronic

Question 15

Severe post-op pain = ?

Answer 15

diamorphine aka. heroin

more lipophilic than morphine

Question 16

Naturally occurring, weaker opioid for mild/moderate pain?

Answer 16

codeine

orally

Question 17

semi-synthetic derivatives of codeine with higher potency…

Answer 17

oxycodone

hydrocodone

Question 18

75-100-fold more potent tan morphine

Answer 18

fentanyl

Question 19

given IV to provide analgesia in maintenance anaesthesia

Answer 19

fentanyl

Question 20

given for acute pain, especially in labour

Answer 20

pethidine

Question 21

Why is pethidine not suitable for chronic pain control?

Answer 21

rapid onset but short duration

Question 22

Partial against for patient-controlled chronic pain; injection or sublingually

Answer 22

buprenorphine - slow onset but long duration of action

Question 23

Which opioid receptor agonist should you avoid in patients with epilepsy?

Answer 23

tramadol

Question 24

what is the plasma 1/2-life of methadone?

Answer 24

> 24hrs

Question 25

uses for methadone?

Answer 25

chronic pain in terminal cancer

assists with withdrawal from strong opioids e.g. heroin

Question 26

opioid antagonist used to reverse opioid toxicity

Answer 26

naloxone

Question 27

Newborn baby with opioid toxicity - potential iatrogenic cause and treatment?

Answer 27

giving mother pethidine during labour

give baby naloxone

Question 28

difference between naltrexone and naloxone?

Answer 28

naltrexone can be given orally and has much longer 1/2 life

Question 29

drugs to reduce GI effects of surgical and chronic opioid use

Answer 29

alvimopan

methylnaltrexone

Question 30

why is paracetamol not classed as an NSAID?

Answer 30

no anti-inflammatory activity and only acts centrally

Question 31

non-selective NSAIDs inhibit COX-1 - why is this an issue if used long term?

Answer 31

PGE2 is produced by COX-1 protects against the acidic nature of stomach = lack of PGE2 = stomach ulcer

Question 32

disadvantage of COX-2 inhibitors?

Answer 32

prothrombotic

Question 33

how do gabapentin and pregabalin work?

Answer 33

reduce cell surface expression of Ca2+ channels which have been unregulated in damaged sensory neurones
this decreases neurotransmitter = nociceptive signal terminates.

Question 34

How does amitriptyline work?

Answer 34

acts centrally by decreasing re-uptake of noradrenaline