Pain Medicine

Question 1

Which agent is used in PCAs? what would determine your choice?

Answer 1

oxycodone/morphine (intermediate acting)
fentanyl
buprenorphine

shift towards oxycodone

• works faster
• half life similar to morphine, 1.5x more potent

fentanyl

• better over long time
• worsening pain, evidence (fentanyl, remifentanyl, sufentanyl) can contribute to hyperalgesia

Buprenorphine
- advantages in non-opoid naive patients
- maintaining one type of opioid throughout patient journey
- used in community for chronic pain (useful for neuropathic) and or opioid substitution therapy (e.g. methadone)
- kappa antagonism properties, slighter safer in terms of sedation/resp depression
- avid mew opioid receptor binder, means don’t use additional effect of other opioids
- analgesia ceiling effect initial concern but not reflected in study
-

Question 2

What sort of pain relief would you use in a previous opioid/methamphetamine user?

Answer 2

• minimal change
• can withdraw from these agents and can worsen pain scores
• nocioceptive pain vs neuropathic pain

Turn to adjuncts
Lidocaine

Ketamine

• neuropathic pain features
• good evidence in acute pain - mechanisms with NMDA receptor antagonism, reduction of hyperalgesia
• side effects: dissociative effects (common), hallucinations, bad dreams
• worsen psychotic state
• racemic mixture, R-antamer has less psychotropic effects

Gabapentanoids

Methadone
- additional NMDA receptor activity

Question 3

In a patient with ongoing pain on the wards what would you use?

Answer 3

Sustained release opioids 
Tramadol 
Targin 
Tapentadol 
slow release (tapentadol SR -palexia) 
- mew receptor 0.3 opioid activity 
- designed to enhance facilitation of noradrenaline desensitisation at spinal cord level
- serotonergic effects (can cause serotonin syndrome but less than tramadol) 
- people with mixed pain states aides

if opioid naive ANZCA have stated sustained release has shown negative impacts.
- try not to discharge on sustained release opioids