Pain Therapeutics Flashcards
What is the role of the NMDA receptor in pain?
the NMDA receptor has a higher threshold than then AMPA receptor - it is only activated with a prolonged stimulus - it has a magnesium ion blocking the channel and when it is displaced it causes cellular remodelling - this is involved in opioid resistance
What is the primary site of action for opioids?
the spinal cord - presynaptically to decrease neurotransmitter release and postsynaptically to hyperpolarise dorsal root neurons
What is the role of the descending noradrenergic and 5-HT neurons from the RVM to the dorsal horn?
inhibition of pain
How does amitryptilline (a tricyclic antidepressant) act as an analgesic?
it is a 5-HT reuptake inhibitor that works at the spinal cord independently of the opioid receptor
How does gabapentin and zirconotide act as an analgesic?
binds to the N-type voltage gated calcium channel to anatagonise transmission of pain - used for chronic pain or to reduce the dose or morphine required
What is the role of the periaqueductal grey area?
descending pathway that blocks pain transmission - activated by endogenous opioids
How does pain cause a cardiovascular response?
the periaqueductal grey area is associated with CV centre to cause hypertension, tachycardia and vasoconstriction
What does an absence of the Nav1.7 receptor cause?
an absence of pain
What does a genetic mutation in COMT cause?
a lack of ability to block pain due to decreased ability of NA to have antinociceptive effects
What does a mutation in CACNG2 cause?
susceptibility to chronic pain
What does a deficiency of CYP2D6 cause?
an inability to convert codeine to morphine
What are the main analgesic medications?
opioids, paracetamol, aspirin, NSAIDs
What are the side effects of opioids?
- ventilatory depression
- drowsiness and sedation
- postoperative nausea and vomiting
- pruritus
- urinary retention
- constipation
- delay hospital discharge
What is multimodal analgesia?
using multiple different analgesics to reduce the dose of opioids required to minimise side effects
What is the mechanism of action of lignocaine?
blocks sodium channels to block nerve transmission
