6. Pain Control Flashcards
Explain how TCAs help control pain.
- increases serotonin/NE in synapse by inhibiting reuptake
- for chronic pain because it take 1-3 weeks to work
TCAs for pain control are most effective for which medical condition?
diabetic neuropathy
Why are antidepressants, alpha adrenergic agonist and opiods good for pain control?
- because NE and serotonin are pain mediators
- they inhibit pain signals from reaching the higher levels of the brain
What is the MOA of alpha adrenergic agonists for pain control?
- they stimulate alpha-adrenoreceptors in the brainstem
- this activates inhibitory neurons –> reduces sympathetic outflow of CNS–> prevents pain signal transmission
What is neuropathic pain triggered by? Mediated by?
- Triggered by spontaneous peripheral nerve activity
- Mediated by sodium channels
What medication classes dampen neuropathic pain? (peripheral sensitivity)
- carbamazepine
- TCAs
- Topiramate
- Lidocaine
Describe the MOA of carbamazepine.
What should you monitor while on this therapy?
- limits the influx of sodium ions across the cell membrane –> decreases neuropathic pain
- mainly used as an anticonvulsant
- monitor bloods levels
Describe the MOA of topiramate.
What should you monitor while on this therapy?
- limits influx of sodiums ions across the cell membrane
- antagonizes glutamate receptors
- mainly used as an anticonvulsant
- monitor electrolytes and kidney function
What are the common SEs of topiramate?
- dizziness
- ataxia
- somnolence
- psychomotor slowing
- paresthesia
- weight loss
Describe the MOA of lidocaine.
- reduces the signal from small afferent nerve fibers by blocking voltage-gated sodium channels.
- this decreases membrane permeability
- usually a gel or transdermal patch
What are the SEs of lidocaine?
- arrythmias
- seizure
- coma
- respiratory depression
- death
What causes central sensitivity? Where does it occur?
- caused by increased calcium transport which cause spontaneous impulses (APs) –> pain message sent to brain
- occurs in the dorsal horn of the spinal cord
Which medications help with central sensitivity by decreasing calcium channel activity?
- gabapentin
- pregabalin
How do NMDA antagonists help with central sensitivity?
- they decrease nerve impulses
Name 3 NMDA antagonists.
Which kind of sensitivity are they used for?
- ketamine
- dextromethorphan
- methadone
- central senstivity
What is the MOA of ketamine?
- decreases central sensitization and modulation by lowering the threshold for nerve transduction
- also reduces the effects of substance P
- targets opiod receptors, Na and K channels to reduce pain
- at high doses, stimulates mu receptors
What is the common SE of ketamine?
local skin reactions
What is the more serious SE of dextromethorphan?
serotonin syndrome (when combine with other antidepressants)
What is the MOA of methadone?
- it is a mu and delta opiod agonist
- but ALSO blocks the NMDA receptor and inhibits the reuptake of NE
Why are there less SEs with methadone than with other opiods?
- because there are no active metabolites
Methadone is lipophilic. Why is this a good thing?
- excellent absorption
- crosses the BBB rapidly
- good distribution in muscle and fat
- high bioavailability
