Opioid & Non-opioid analgesics Flashcards

1
Q

What are the 4 steps of pain:

A

transduction
transmission
modulation
perception

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2
Q

What is transduction?

A

Noxious stimuli stimulates an action potential

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3
Q

What nerve fibers are involved in pain transduction?

A

C fibers: slow pain, dull, poorly localized from free nerve endings
A-delta fibers: fast pain, sharp, well localized from specialized receptors

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4
Q

How does inflammation contribute to pain?

A

Reduced threshold to pain stimulus (allodynia)
Increased reposed to pain stimulus (hyperalgesia)

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5
Q

What drugs target pain transduction?

A

NSAIDs
local anesthetics
steroids
antihistamines
opioids

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6
Q

What is pain transmission?

A

Pain signal is relayed via three-neuron pathway along the spinothalamic tract.

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7
Q

Where does the first order neuron originate and travel to? Where is the cell body?

A

periphery to dorsal horn
cell body in dorsal root ganglion

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8
Q

Where does the second order neuron originate and travel to? Where is the cell body?

A

dorsal horn to thalamus
cell body in dorsal horn

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9
Q

Where does the third order neuron originate and travel to? Where is the cell body?

A

thalamus to cerebral cortex
cell body in thalamus

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10
Q

What drugs target pain transmission?

A

local anesthetics

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11
Q

What is pain modulation?

A

Pain signal is modified (augmented or inhibited) as it travels to cerebral cortex.

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12
Q

What is the most important site of pain modulation?

A

Substantia gelatinosa in the dorsal horn, aka Rexed lamina 2 & 3

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13
Q

When is pain inhibited due to modulation?

A

spinal neurons release GABA and glycine (inhibitory ntms)
descending pain pathway releases NE, serotonin, endorphins

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14
Q

When is pain augmented by modulation?

A

central sensitization
wind-up

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15
Q

What drugs target pain modulation?

A

Neuraxial opioids
NMDA antagonists
Alpha 2 agonists
AchE inhibitors
SSRIs
SNRIs

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16
Q

What is pain perception?

A

describes feeling of pain due to afferent pain signals in the cerebral cortex and limbic system

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17
Q

What drugs target pain perception?

A

general anesthetics
Alpha 2 agonists
opioids

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18
Q

Discuss opioid receptor agonism:

A
  1. Opioid binds receptor
  2. G protein is activated
  3. Adenylate cyclase is inhibited
  4. cAMP production is decreased
  5. Ca conductance is decreased
  6. K conductance is increased
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19
Q

List opioid receptor types and their endogenous opioids:

A

Mu - endorphins
Delta - enkephalins
Kappa - dynorphins

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20
Q

What side effects do Delta receptors produce?

A

respiratory depression
urinary retention
pruritus

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21
Q

What side effects do Kappa receptors produce?

A

respiratory depression?
sedation, dysphoria, hallucinations, delirium
miosis
diuresis
anti shivering

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22
Q

What side effects do Mu 1 receptors produce

A

*analgesia (supra spinal and spinal)
*bradycardia
miosis
low abuse potential
euphoria
hypothermia
urinary retention

23
Q

What side effects do Mu 2 receptors produce?

A

*analgesia (only spinal)
*bradycardia
*respiratory depression
*constipation
*physical dependence

24
Q

What side effects do Mu 3 produce?

A

immune suppression

25
Q

Where are opioid receptors located?

A

Brain: periaquaductal gray, locus coeruleus, rostral ventral medulla
Spinal cord: primary afferent neurons in dorsal horn and interneurons
Peripheral: sensory neurons and immune cells

26
Q

What ventilation effects accompany opioid administration?

A

CO2 curve shifts right
decreased response to CO2
decreased RR
increased Vt
increased PaCO2 -> increased ICP if ventilation not maintained

27
Q

What pupil effects accompany opioid administration?

A

miosis due to PNS stimulation of ciliary ganglion and oculomotor nerve (CN3)
tolerance to miosis does not develop

28
Q

What N/V effects accompany opioid administration?

A

increased stimulation of the chemoreceptor trigger zone of the area postrema in medulla
possible interaction with the vestibular apparatus

29
Q

What SSEP effects accompany opioid administration?

A

minimal effect on evoked potentials

30
Q

What CV effects accompany opioid administration?

A

bradycardia
minimal BP reduction in healthy patient
dose dependent vasodilation
baroreceptor reflex NOT affected
contractility NOT affected
depression can occur if given with N2O

31
Q

What GI effects accompany opioid administration?

A

increased biliary pressure due to Sphincter of Oddi contraction (reverse: naloxone or glucagon)
(meperidine affects least)

prolonged gastric emptying

slowed peristalsis -> constipation

32
Q

What GU effects accompany opioid administration?

A

urinary retention due to detrusor muscle relaxation (contraction needed to pass urine into ureters)

urinary sphincter contraction

33
Q

What immunologic effects accompany opioid administration?

A

histamine release: morphine, meperidine, codeine
inhibition of cellular and humor immune function
suppression of natural killer cell function

34
Q

What thermoregulation effects accompany opioid administration?

A

hypothalamic temperature set point is reset -> decreased core body temperature

35
Q

What gender differences occur with morphine administration?

A

in women:
greater analgesic potency
slower onset of action
longer duration of action
lower postoperative opioid consumption

36
Q

Relative potency of opioids:

A
37
Q

Discuss Buprenorphine

A

partial Mu agonist
greater analgesia than morphine
narcan reversal difficult due to high affinity for mu receptor
long duration - 8 hours
available via transdermal route

38
Q

Discuss Nalbuphine

A

Mu antagonist
Kappa agonist
similar analgesia to morphine
can be reversed by narcan
doesn’t increase HR, BP, PAP, or RAP
useful with history of heart disease

39
Q

Discuss butorphanol

A

Mu antagonist (weak)
Kappa agonist
greater analgesia than morphine
can be reversed by narcan
useful for postop shivering
available via intranasal route

40
Q

Discuss the antagonism properties of naloxone:

A

antagonizes mu (greatest affinity), kappa, and delta opioid receptors

41
Q

What is naloxone used for?

A

prototype opioid antagonist used to reverse opioid-induced respiratory depression
treatment of opioid overdose
reversal of respiratory depression in the neonate whose mother received an opioid

42
Q

What is the dose and duration of action of naloxone?

A

1-4 mcg/kg
duration 30-45 minutes
titrate 20-40 mcg at a time to prevent overshoot
liver metabolism (significant first-pass metabolism)

43
Q

What opioid antagonist is a quaternary amino group? What does this prevent?

A

Methylnaltrexone. Cannot pass BBB, so cannot reverse respiratory depression. Useful in peripheral effects of opioids, such as opioid-induced bowel dysfunction

44
Q

Discuss the opioid antagonist that is similar to naloxone but has a much longer duration of action:

A

Nalmefene
0.1-0.5 mcg/kg
Duration 10 hours
Used to maintain recovering opioid abusers

45
Q

What is the benefit of naltrexone vs naloxone?

A

Naltrexone does not undergo significant first-pass metabolism
Can be given orally
Duration up to 24 hours
Use extended release for alcohol withdrawal treatment
Use to maintain recovering opioid abusers

46
Q

Which partial agonists mechanism of action includes kappa agonism and mu antagonism?

A

nalbuphine
butorphanol

47
Q

Which partial agonists have greater potency than morphine?

A

butorphanol
buprenorphine

48
Q

Which partial agonists partially agonize mu receptors?

A

buprenorphine

49
Q

Which partial agonists can be reversed by naloxone?

A

nalbuphine
butorphanol

(not buprenorphine due to strong affinity mu receptor)

50
Q

Which partial agonist does not increase BP, HR, PAP, or RAP? What patient population are these useful in?

A

nalbuphine
useful in patients with heart disease

51
Q

Which partial agonist can be used for postoperative shivering?

A

butorphanol

52
Q

Which partial agonist is available via transdermal route and has a long duration of action of 8 hours?

A

buprenorphine

53
Q

Which partial agonist is available via intranasal route?

A

butorphanol