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Local + Opioids > Opioids > Flashcards

Opioids Flashcards

1
Q

What are the 4 steps of the pain pathway?

A

Transduction
Transmission
Modulation
Perception

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2
Q

What is transduction?

A

Converts a noxious stimulus into an action potential through the release of various chemicals

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3
Q

What is transmission?

A

The pain signal is relayed through three neurons along the spinothalamic tract (afferent)

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4
Q

What is modulation? Where is the most important site?

A

-Pain is inhibited or augmented as it advances towards the cerebral cortex

-Substantia gelatonisa in the dorsal horn (rexed lamina 2 and 3)

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5
Q

What is Perception?

A

Processing of afferent pain signals in the cerebral cortex and limbic system. How we “feel”

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6
Q

What are nociceptors?

A

Free nerve endings that respond to pain

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7
Q

What are the specialized nociceptors?

A

Merkel’s disks
Ruffini endings
Meissner’s corpuscles
Pacinian Corpuscles

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8
Q

What drugs target transduction?

A

NSAIDS
Local’s
Steroids
Antihistamines
Opioids

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9
Q

How does inflammation contribute to transduction?

A

Allodynia - Reduced threshold to pain

Hyperalgesia - Increased response to pain

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10
Q

What drugs target transmission?

A

Local’s (blocking the nerve)

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11
Q

Where is the first order neuron? Where is the cell body?

A

Periphery to dorsal horn

Cell body in the dorsal root ganglion

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12
Q

Where is the second order neuron? Where is the cell body?

A

Dorsal horn to thalamus

Cell body in the dorsal horn

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13
Q

Where is the third order neuron? Where is the cell body?

A

Thalamus to cerebral cortex

Cell body in the thalamus)

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14
Q

How is pain inhibited during modulation?

A

Spinal neurons release GABA and Glycine

The descending pathway releases NE, serotonin, and endorphins

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15
Q

How is pain augmented during modulation?

A
  1. Central sensitization
  2. Wind-up
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16
Q

What drugs target modulation?

A

Neuraxial opioids
NMDA antagonists
SSRI
SNRI
AchE inhibitors
Alpha 2 agonists

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17
Q

What drugs target perception?

A

General anesthetics
Opioids
Alpha 2 agonists

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18
Q

What type of receptor is the opioid?

A

G linked protein

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19
Q

What are the steps of an opioid binding to the receptor ?

A
  1. Opioid binds to the receptor
  2. G protein is activated
  3. Adenylate cyclase is inhibited
  4. Decreased cAMP
  5. Ca is decreased
  6. K is increased
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20
Q

What are the 4 types of opioid receptors?

A

Mu
Kappa
Delta
ORL-1

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21
Q

What opioid receptor produces the most classic signs of opioid administration?

A

Mu

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22
Q

Where are they located?

A

Brain - Periaqueductal gray, locus coeruleus, rostral ventral medulla

Spinal Cord - Primary afferent neurons in the dorsal horn

Peripheral - sensory neurons and immune cells

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23
Q

What are the precursors to endogenous opioids?

A

Pre-proopiomelanocortin - endorphins (Mu)

Pre-enkephalin - Enkephalins (Delta)

Pre- dynorphin - Dynorphins (Kappa)

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24
Q

Which opioid receptor produces bradycardia?

A

Mu

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25
Q

Which opioid receptor produces diuresis?

A

Kappa

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26
Q

Which opioid receptor does not produce respiratory depression?

A

Kappa

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27
Q

Which opioid receptor produces GI symptoms?

A

Mu

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28
Q

Which opioid receptor does not produce pruritis?

A

Kappa

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29
Q

Which opioid receptor produces antishivering?

A

Kappa

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30
Q

Which opioid receptor does not produce CNS effects?

A

Delta

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31
Q

Which opioid receptor does not produce miosis (pupil constriction?

A

Delta

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32
Q

How does gender play a difference in PK/PD among opioids?

A

Women have a;

Greater analgesic potency
Slower onset of action
Longer duration of action
Lower postoperative opioid consumption

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33
Q

How do opioids affect ventilation ?

A

Shifts response curve to the right and reduces the response to CO

Decreased RR

Increased VT

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34
Q

How do opioids affect pupils?

A

Constriction through stimulation of PNS ciliary ganglion and CN3

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35
Q

How do opioids affect N/V?

A

Increases in the chemoreceptor zone (Medulla)

Possible vestibular apparatus

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36
Q

How do opioids affect SSEP?

A

Minimal effect

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37
Q

How do opioids affect Cardio ?

A

Bradycardia

Hypotension ONLY through histamine release

Baroreceptor not affected

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38
Q

How do opioids affect GI?

A

Contraction of sphincter of Oddi -Increases biliary pressure

Decreased motility

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39
Q

How do opioids affect GU?

A

Urinary retention

Histamine release, suppression of immune function and natural killer T cells

Resets hypothalamic temp set point which decreases core body temp

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40
Q

What are the naturally occurring opioids?

A

Phenanthrene derivatives

Morphine
Codeine which is the precursor to morphine

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41
Q

What are the semisynthetic opioids?

A

Hydromorphone, heroin, naloxone, naltrexone

Thebaine derivative - Oxycodone

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42
Q

What are the synthetic opioids?

A

Piperidines - Meperidine

Phenylpiperidines - Fentanyl, remi, su, al

Diphenylpropylamines - Methadone

43
Q

What is the standard potency all opioids follow?

A

10mg IV morphine

44
Q

Opioid chart

A
45
Q

What are tolerance and dependence most likely related to?

A

Receptor desensitization and increased synthesis of cAMP

Not due to enzyme induction

46
Q

Tolerance develops to all side effects accept…?

A

Miosis and constipation

47
Q

What are the early sign of withdrawal? Late signs?

A

Early - Sweating, insomnia, restlessness

Late - cramping, N/V

48
Q

Timing of withdrawal for fentanyl, morphine, methadone? Chart?

A
49
Q

What opioid is not metabolized by the liver?

A

Remi

50
Q

What opioids have active metabolites?

A

Morphine
Meperidine
Hydromorphone

51
Q

What is the metabolite of morphine? What can it cause?

A

M6G - does not cross BBB

Dialysis patients are unable to secrete M6G

Do not give morphine to renal failure patients AND can cause toxicity with chronic use even with normal renal function

52
Q

What cautions should be taken with meperidine?

A

Reduces seizure threshold

Careful with renal failure and elderly

Don’t use with PCA pump

Histamine release

Antishivering effects

Weak serotonin reuptake inhibitor - careful with MAOI

Anticholinergic effects

53
Q

What class is meperidine? What opioid receptor does it stimulate

A

Synthetic phenylpiperidine

Mu and Kappa

54
Q

What is the half life of meperidine ?

A

15 hours but can take 35 hours.

55
Q

What is the pKa of Alfentanil ? special characteristics?

A

-Weak base - 6.5 pKa

-Fastest onset of action

-90% is non ionied

-Low Vd - since it doesn’t distribute, more goes to the brain

-High protein binding

56
Q

Metabolism of Alfentanil?

A

CYP3A4

Low extraction ratio - erythromycin inhibits the metabolism

No active metabolite so renal function does not matter

57
Q

Special characteristics of Remifentanil ?

A

Similar potency to fentanyl

Context sensitive half time is about 4 minutes

Calculated on LEAN body weight, does not distribute to fat

Small Vd due to fast clearance of Esterases

Causes opioid induced hyperalgesia

Can cause muscle weakness due to being mixed with glycine

58
Q

Does a pseudocholinesterase deficiency affect the metabolism of remifentanil?

A

No

59
Q

How is methadone prepared? When is it used?

A

As a racemic mixture

Used for chronic pain, opioid abuse, and cancer pain

60
Q

How does methadone decrease pain? Three ways

A
  1. Mu agonist
  2. NMDA antagonist
  3. Inhibits reuptake of MAO’s
61
Q

How is methadone metabolized? Active metabolite?

A

Oral - Bioavailability 80%

Duration of action is 3-6 hours

Chronic use prolongs duration of action

No active metabolite

62
Q

How does methadone prolong QT?

A

Inhibits the delayed rectifier K channel

63
Q

Facts about Oliceridine

A

Brand new selective Mu receptor

Do not exceed 27mg

Increases all symptoms - seizure risk, QT prolongation, hypotension, significant respiratory depression, GI obstruction

64
Q

How do opioids affect skeletal muscle? Which ones?

A

Rapid IV infusion causes chest wall rigidity and issues with the larynx

-More common with potent compounds such as sufentanil, remi, fentanyl, and alfentanil

Likely from the Mu receptor

Best treatment is to paralyze and intubate

Naloxone does work

65
Q

What complications develop from a stiff chest?

A

-Increased pressure, CVP, RAP, PVR

-Increased O2 consumption

Hypoxia, Hypercapnia

Decreased SvO2, FRC, MV, FRC

66
Q

Special characteristics of partial opioid agonists?

A

-Produce analgesia with reduced symptoms

-Lower risk of dependence

-Have a ceiling effect and reduces the efficacy of previous opioids

-Can cause acute opioid withdrawal

67
Q

Special characteristics of Buprenorphine?

A

Partial Mu agonist

Greater analgesia than morphine

Not reversed by naloxone

Long duration and available in transdermal route

68
Q

Special characteristics of Nalbuphine?

A

Kappa agonist + Mu antagonist

Similar analgesia to morphine

Reversed by Naloxone

Useful in heart disease because does not cause many cardiovascular effects

69
Q

Special considerations for butorphanol?

A

Kappa agonist + Mu antagonist

Greater analgesia than morphine

Reversed by naloxone

Useful for postop shivering

Transdermal route

70
Q

How does Naloxone work?

A

Antagonizes all opioid receptors but has the greatest affinity at the Mu receptor

71
Q

Key facts about Naloxone

A

1-4mcg/kg

Duration 30 minutes

Liver metabolism with significant first pass

ACTIVATES THE SNS

Can cross the placenta and can cause acute opioid withdrawal in the fetus

Anti pruritis

72
Q

Key facts about Methylnaltrexone?

A

Does not cross the BBB so does NOT reverse respiratory depression

Useful in bowel dysfunction

73
Q

Key facts about Nalmefene?

A

Similar to Narcan however much longer duration of action, 10 hours

74
Q

Key facts about Naltrexone?

A

Can be given orally and does not undergo first pass metabolism

Can give extended release

Good for abusers

75
Q

What is the gold standard for postoperative opioid delivery?

A

PCA due to increased patient satisfaction and better pain control

Incidence of respiratory depression is NOT increased

76
Q

Key facts about PCA pumps

A

-Demand should provide pain relief without toxicity

-Lockout interval is based on the time it takes to reach an effective plasma concentration

-Basal rate is used for chronic pain, not postoperative

-Use scheduled NSAIDS

-END TIDAL is the best monitor

-Morphine is not used due to the M6G metabolite

-Can use in pregnancy

77
Q

What is the most important site of pain modulation?

A

Dorsal horn of the spinal cord - Rexed lamina 2 and 3

78
Q

What is the process of transduction?

A

Injured tissues release various chemicals that release proinflammatory compounds

Peripheral nerves transduce this chemical soup into an action potential

79
Q

What type of nerves transmit pain?

A

A - delta fibers (fast sharp pain, well localized)

C - fibers (slow, dull pain)

80
Q

What is the role of inflammation in pain transduction?

A

-Reduces the threshold to a pain stimulus (allodynia)

-Increases the response to a pain stimulus (hyperalgesia)

81
Q

What is the process of pain transmission?

A

Pain signal is sent through the afferent pain pathway along the spinothalamic tract

82
Q

What are the three neurons in the pain transmission pathway?

A

First - periphery to dorsal horn in the dorsal root ganglion

Second - dorsal horn to the thalamus, cell body in the dorsal horn

Third - thalamus to cerebral cortex, cell body in the thalamus

83
Q

Where is the most important site of pain modulation?

A

Substantia gelatinosa in the dorsal horn (rexed lamina 2 + 3)

84
Q

Where is the descending inhibitory pain pathway begin and end?

A

being sin the periaqueductal gray and medulla. Projects to the substantia gelatinosa

85
Q

When does pain inhibition occur?

A

-Spinal neurons release GABA and Glycine

-Descending pathway release NE, Serotonin and endorphins

86
Q

How is pain augmented?

A

Wind up and central sensitization

87
Q

Where does the perception of pain occur?

A

Afferent pain signals in the cerebral cortex and limbic system

88
Q

What is unique to Kappa?

A

Anti shivering
Diuresis
Dysphoria
Delirium and Hallucinations

89
Q

How do opioids affect myocardial function?

A

-Doesn’t unless combined with N20

90
Q

How can opioids affect ICP?

A

May increase due to an increase in CO2

91
Q

How do opioids affect the pupil?

A

Edinger Westphal nucleus stimulation

Increases PNS stimulation of ciliary ganglion and oculomotor nerve CN3)

Pupil constriction

92
Q

How do opioids affect the bladder?

A

Causes detrusor relaxation and urinary sphincter constriction

93
Q

How does methadone reduce pain?

A

Mu receptor agonist

NMDA antagonist

Inhibits MAO

94
Q

Opioid with the greatest Vd? Least?

A

Greatest - Fentanyl

Least - Remi

95
Q

Which opioid is the most likely to prolong QT?

A

Methadone

96
Q

Which opioid receptor can causes skeletal muscle rigidity ?

A

Mu

97
Q

What are characteristics of opioid agonists - antagonists ?

A

Produce pain relief with reduced risk of respiratory depression

Have a ceiling effect

Reduce the efficacy of previous opioids

Can cause acute opioid withdrawal

Can cause dysphoric reactions

Low risk of dependence

98
Q

What are some side effects of naloxone?

A

SNS activation - PULMONARY edema

N/V

Crosses BBB - fetal opioid withdrawal

99
Q

Which opioid antagonist does not cross the BBB and does not reverse respiratory depression?

A

Methylnaltrexone

100
Q

Which opioid antagonist is the longest acting ? What’s it used for?

A

Naltrexone - does not undergo first pass metabolism

-Alcohol withdrawal/ opioid abusers

101
Q

What are two important excitatory neurotransmitters in the dorsal horn?

A

Glutamate and substance P

102
Q

What nerve bypasses the spinal cord?

A

Trigeminal nerve

103
Q

What two medications help prevent hyperalgesia related to D/C of remi?

A

Ketamine and magnesium

Local + Opioids (3 decks)

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