6. Pain Control

Question 1

Explain how TCAs help control pain.

Answer 1

• increases serotonin/NE in synapse by inhibiting reuptake

- for chronic pain because it take 1-3 weeks to work

Question 2

TCAs for pain control are most effective for which medical condition?

Answer 2

diabetic neuropathy

Question 3

Why are antidepressants, alpha adrenergic agonist and opiods good for pain control?

Answer 3

• because NE and serotonin are pain mediators

- they inhibit pain signals from reaching the higher levels of the brain

Question 4

What is the MOA of alpha adrenergic agonists for pain control?

Answer 4

• they stimulate alpha-adrenoreceptors in the brainstem

- this activates inhibitory neurons –> reduces sympathetic outflow of CNS–> prevents pain signal transmission

Question 5

What is neuropathic pain triggered by? Mediated by?

Answer 5

• Triggered by spontaneous peripheral nerve activity

- Mediated by sodium channels

Question 6

What medication classes dampen neuropathic pain? (peripheral sensitivity)

Answer 6

• carbamazepine
• TCAs
• Topiramate
• Lidocaine

Question 7

Describe the MOA of carbamazepine.

What should you monitor while on this therapy?

Answer 7

• limits the influx of sodium ions across the cell membrane –> decreases neuropathic pain
• mainly used as an anticonvulsant
• monitor bloods levels

Question 8

Describe the MOA of topiramate.

What should you monitor while on this therapy?

Answer 8

• limits influx of sodiums ions across the cell membrane
• antagonizes glutamate receptors
• mainly used as an anticonvulsant
• monitor electrolytes and kidney function

Question 9

What are the common SEs of topiramate?

Answer 9

• dizziness
• ataxia
• somnolence
• psychomotor slowing
• paresthesia
• weight loss

Question 10

Describe the MOA of lidocaine.

Answer 10

• reduces the signal from small afferent nerve fibers by blocking voltage-gated sodium channels.
• this decreases membrane permeability
• usually a gel or transdermal patch

Question 11

What are the SEs of lidocaine?

Answer 11

• arrythmias
• seizure
• coma
• respiratory depression
• death

Question 12

What causes central sensitivity? Where does it occur?

Answer 12

• caused by increased calcium transport which cause spontaneous impulses (APs) –> pain message sent to brain
• occurs in the dorsal horn of the spinal cord

Question 13

Which medications help with central sensitivity by decreasing calcium channel activity?

Answer 13

• gabapentin

- pregabalin

Question 14

How do NMDA antagonists help with central sensitivity?

Answer 14

• they decrease nerve impulses

Question 15

Name 3 NMDA antagonists.

Which kind of sensitivity are they used for?

Answer 15

• ketamine
• dextromethorphan
• methadone
• central senstivity

Question 16

What is the MOA of ketamine?

Answer 16

• 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

Question 17

What is the common SE of ketamine?

Answer 17

local skin reactions

Question 18

What is the more serious SE of dextromethorphan?

Answer 18

serotonin syndrome (when combine with other antidepressants)

Question 19

What is the MOA of methadone?

Answer 19

• it is a mu and delta opiod agonist

- but ALSO blocks the NMDA receptor and inhibits the reuptake of NE

Question 20

Why are there less SEs with methadone than with other opiods?

Answer 20

• because there are no active metabolites

Question 21

Methadone is lipophilic. Why is this a good thing?

Answer 21

• excellent absorption
• crosses the BBB rapidly
• good distribution in muscle and fat
• high bioavailability