Block 3 Lecture 4 -- Pain Pathways and Non-opioid Analgesics, and Lecture 5 Opioids Flashcards
When is amantadine preferred?
new patients with mild symptoms
What are the chemical mediators of pain?
1) bradykinin
2) 5-HT
3) neuropeptides
4) ATP, K+
5) chemokines
6) PGE2
7) Na, Ca, Glu ion channels
8) ASICs
9) TRPV1
What neuropeptides mediate pain?
CGRP: calcitonin-gene-related peptide– especially in migraine
What is TRPV1?
transient receptor potential vanilloid-1 channel– Ca-permeable ionotrope activated by protons
Where are protons as a source of pain produced?
1) tumor
2) heat
3) inflammation
4) capsaicin
5) gaseous anesthetics
What are the 3 important factors to treating pain?
1) site of drug action
2) timing
3) nature of pain
What drugs target the site of pain initiation?
1) methylene blue
2) ASA, NSAIDs
What drugs target the transmission pathway of pain?
local anesthetics
What is methylene blue?
neurotoxicant; injection destroys nerve endings
What drugs target the spinal cord?
1) topical counterirritants
2) transcutaneous electrical nerve stimulation
What is capsaicin’s MoA? Any counseling points?
TRPV1 agonist
2-4 weeks for max efficacy
How do topical counterirritants work?
reduce referred pain in same dermatome
What things act on the spinothalamic tract fibers to reduce pain?
1) EtOH (kill fiber)
2) anterolateral cordotomy
What things act on the spinal cord and brain to reduce pain?
opioids
What are the benefits of pre-emptive acute pain treatment?
decreases risk of progression from acute to chronic pain
What things are known pruritogens?
1) histamines
other chemicals, drugs
What mediates itch?
MrgrprA3 (mas-related GPCR)
- not a sub-modality of pain
- ALST
Differentiate COX-1 vs. COX-2 structure.
COX-2 has 523 Val (allows larger side chain)
COX-1 has Ile 523
What are prostanoids?
all the products of COX pathway
What are eicosanoids?
20C metabolites of arachidonic acid
What are the effects of PGE2?
1) pain
2) inflammation
3) inhibit acid secretion
4) increase GI mucous, bicarb
5) maintain renal blood flow; increase Na/H2O excretion
What are the effects of TXA2?
1) vasoconstriction
2) platelet aggregation
What are the effects of PGI2?
1) vasodilation, esp. mucosal
2) increase GI mucous, bicarb
3) inhibit GI acid secretion
4) maintain renal blood flow; increase Na/H2O excretion
5) platelet disaggregation
What are the major COX-1 products?
PGE2 + TXA2