Opioids Flashcards

1
Q

What are the medical uses of opioids?

A

Pain = anti-nociceptive
Safe and effective when used appropriately

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2
Q

How do opioids block pain?

A

They block afferent transmission in the spinal cord/brainstem
Periaqueductal gray

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3
Q

What is a lethal mix of drugs?

A

Opioids and sedatives

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4
Q

What are the 3 major sources of opioids?

A

Natural
Semi-synthetic
Synthetic

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5
Q

What are natural sources of opioids?

A

Opium - alkaloid-laden latex
Morphine, codeine

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6
Q

What are semi-synthetic sources of opioids?

A

Heroin, hydrocodone, hydromorphone, oxycodone, krokodil
Buprenorphine, etorphine

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7
Q

What are synthetic sources of opioids?

A

Methadone, meperidine
Tramdol
Fentanyl

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8
Q

What are major narcotics?

A

Morphine (10%)
Codeine (0.5%)

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9
Q

What is more potent: morphine or opium?

A

Morphine is 10x more potent than opium

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10
Q

What does CYP2D6 convert codeine to in the brain and liver?

A

Morphine

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11
Q

What is the result of deficient 2D6?

A

Codeine has no effect

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12
Q

What is the result of overactive 2D6?

A

Morphine intoxication

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13
Q

How are semi-synthetic opioids produced?

A

Produced by modifying a naturally-derived chemical

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14
Q

What makes heroin 10x more lipophilic than morphine?

A

Two acetyl groups

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15
Q

What is naloxone?

A

Opioid receptor antagonist

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16
Q

What is methadone?

A

mew agnoist

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17
Q

When was naloxone synthesized?

A

1960s

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18
Q

What does naloxone do?

A

Reverses morphine effects

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19
Q

What did Pert and Snyder discover in the brain?

A

Opioid receptors

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20
Q

What are the 4 classes of pre and post-synaptic opioid receptors?

A

mew, delta, kappa, and ORL-1

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21
Q

What do pre-synaptic opioid receptors do?

A

Modulate NT release

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22
Q

What do post-synaptic opioid receptors do?

A

Alter membrane potential

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23
Q

How were opioid receptors discovered?

A

Radioligand binding in brain tissue slices

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24
Q

Where were opioid receptors found in the brain?

A

Striatal area
Lateral aspect of medial nucleus
Amygdala
Dorsal pons
Periaqueductal gray
Spinal cord

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25
Q

How many endogenous opioids are known?

A

18 peptide ligands and endorphins

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26
Q

What are endogenous opioids involved in?

A

Pain, emotional responses, euphoria, eating, stress, seizures, and alcohol dependence

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27
Q

Where are MOR (mew opioid receptors) expressed?

A

VTA, NAc
PAG
Hypothalamus
LC
Brainstem
Pupils
GI tract

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28
Q

What binds MOR?

A

Most opioids

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29
Q

What are MOR involved in?

A

Reward, addiction
Analgesia
Euphoria
Anxiolytic
Respiration, BP
Nausea
Itch
Constriction
Constipation

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30
Q

Where are DOR (delta opioid receptors) expressed?

A

Neocortex
Striatum
NAc
Substantia nigra
Olfactory bulb

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31
Q

What are DORs bound by?

A

Enkephalins

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32
Q

Where are KORs (kappa opioid receptors) expressed?

A

Pituitary
Hypothalamus
PAG
Spinal cord
Others

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33
Q

What are KORs bound by?

A

Endorphins, dynorphins, PCP, ketamine

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34
Q

Where are orphan opioid receptors expressed?

A

Limbic system
Spinal cord

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35
Q

What are orphan opioid receptors bound by?

A

Buprenorphrine

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36
Q

How potent is fentanyl?

A

100x more potent than morphine
40-50x more potent than heroin
Highly lipophilic

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37
Q

Why are fentanyl derivatives even more potent?

A

Increased affinity for mu receptors + enhanced entry into the brain = higher potency

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38
Q

How are opioids distributed?

A

Lipid solubility
Liver
Lungs
Spleen
GI tract
Brain

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39
Q

How are opioids absorbed?

A

Inhalation
Injection
Ingestion
Insufflation
Sublingual
Rectal

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40
Q

What is the chasing the dragon method?

A

Heat up on tin foil and inhale the fumes
More commonly smoked in a pipe

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41
Q

What is chasing the dragon linked to?

A

Leukoencephalopathy
Spongiform brain tissue with holes
Progresses to ataxia, apathy, akathisia, inability to speak or move
Appears like metal toxicity

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42
Q

How is heroin injected?

A

Mixed with some water on a spoon, acid or heat might help dissolve, drawn up through a cotton ball to remove particulates

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43
Q

Why does injecting heroin leave track marks?

A

Damage to vessels by the needle
Uneven blood flow, thrombosis, clots form
Vessels collapse, need to find a new one

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44
Q

Where are opioids metabolized?

A

Brain
Liver

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45
Q

How are opioids excreted?

A

Kidneys
Feces

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46
Q

What are the pharmacokinetics of heroin?

A

Faster distribution to the brain = higher potency
May be snorted
Metabolized to morphine in the brain
Two intermediates = 3-MAM and 6-MAM
6-MAM binds MOR but 3-MAM does not
6-MAM is not naturally occurring

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47
Q

What are the psychological effects of acute opioid use?

A

Euphoria, well-being, tranquillity
Mental clouding, impaired judgement, decreased attention and memory

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48
Q

What are the brain effects of acute opioid use?

A

Reduced pain
Inhibited cough and slowed respiration
Increased sedation
Constricted pupils

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49
Q

What are the cardiovascular effects of acute opioid use?

A

Dilated blood vessels and lowered blood pressure

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50
Q

What are the effects of acute opioid use on the skin?

A

Lowered body temp
Flushed skin
Itching

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51
Q

What are the effects of acute opioid use on muscles?

A

Muscle relaxation

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52
Q

What are the effects of acute opioid use on the renal system?

A

Decreased urination

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53
Q

What are the effects of acute opioid use on the GI tract?

A

Decreased GI movements and secretions
Constipation

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54
Q

What are the effects of acute opioid use on the reproductive system?

A

Decreased testosterone and estrogen
Lowered sperm production
Diminished libido

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55
Q

How does acute opioid use affect the medulla?

A

Lowers BP
Hypotension, bronchoconstriction, itching from histamine release

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56
Q

Why do the pupils constrict with opioid use?

A

mu/kappa receptors in oculomotor nucleus

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57
Q

What is neonatal abstinence syndrome?

A

Babies are irritable, vomit, diarrhea, seizures, in respiratory distress due to withdrawal

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58
Q

How is NAS treated?

A

Physical contact reduces hospital time

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59
Q

What comes from separate Opr genes?

A

Mu, delta, kappa opioids receptors

60
Q

What do ORL orphan display in relation to other opioid receptors?

A

Structural homology

61
Q

What are most opioid effects due to?

A

Mu receptor

62
Q

What do all endogenous opioids contain?

A

N-terminal tyrosine residues

63
Q

What does morphine mimic?

A

The structure of tyrosine

64
Q

What type of receptor are all opioid receptors?

A

GPCRs, linked via Gi/o

65
Q

What does ligand binding on opioid receptors trigger?

A

alpha-GTP loading

66
Q

Which subunits dissociate after ligands bind opioid receptors?

A

Aloha and betagamma subunits

67
Q

What does alpha-GTP inhibit?

A

Inhibits adenylate cyclase which reduces [cAMP] which inhibits protein kinase A

68
Q

What does alpha-GTP activate?

A

PLCbeta and MAPK pathways

69
Q

What do beta gamma subunits activate (opioids)?

A

Activates GIRK3 causing hyperpolarization

70
Q

What do beta gamma subunits block?

A

Ca channels causing reduced intracellular Ca and suppressing neurotransmitter release

71
Q

What does chronic exposure to morphine result in?

A

G-protein coupled receptor kinase mediated phosphorylation of opioid receptors and binding of beta-arrestin which leads to desensitization

72
Q

What is biased agonism?

A

Differential activation of signalling pathways by OR ligands

73
Q

What is classic opioid signalling due to?

A

Biased G-protein effects

74
Q

What does morphine keep low?

A

Receptor phosphorylation

75
Q

What happens when opioids like fentanyl produce high receptor phosphorylation

A

Receptor internalization, increase tolerance and dependence

76
Q

What do non-synonymous mutations in MOR affect?

A

Signalling and function

77
Q

What do non-synonymous mutations in MOR affect?

A

Signalling and function

78
Q

What receptors are involved in opioid-mediated analgesia?

A

MORs

79
Q

Where are MORs found in the path pathway?

A

Thalamus, PAG, rostroventral medulla, dorsal horn of spine

80
Q

What is the pain pathway?

A

Cortex -> thalamus (doesn’t need to tho) -> PAG -> RVM -> DHs

81
Q

What is the mechanism of opioid-mediated analgesia?

A

Activation of MOR on GABA-ergic RVM interneurons

82
Q

What does tonic firing from the RVM to the dorsal horn do?

A

Sets the pain afferent threshold

83
Q

What does the activation of MOR on GABA-ergic RVM interneurons do?

A

Reduces inhibition of RVM OFF projecting cells to the spinal cord
Elevated signaling out of the RVM to the spinal cord
Decreased afferent pain transmission into the spine

84
Q

What does activation of MOR on RVM ON projecting cells to the spinal cord do?

A

Decreases outputs to the dorsal horn of the spine, adding to analgesic effect

85
Q

What plays an indirect role in modifying pain transmission?

A

The amygdala

86
Q

What happens in the dorsal horn during opioid-mediated analgesia?

A

Pre-synaptic MOR activation of afferent pain neurons reduces NT release and pain transmission

87
Q

What neurotransmitters play important roles in opioid-mediated pathways in addictiveness?

A

Glu, DA, GABA

88
Q

Are NMDARs or AMPARs more important in opioid-mediated pathways in addictiveness?

A

AMPARs

89
Q

What is the role of hippocampal mu receptors in opioid-mediated pathways in addictiveness?

A

Disinhibition of CA1 and dentate gyrus cells via GABA-ergic interneurons
Astrocytes also express MORs and activation causes Glu release onto CA1 neurons
Associate conditioning

90
Q

What do D1-like receptors in the NAc co-express?

A

Dynorphin

91
Q

What do D2-like receptors in the NAc co-express?

A

Enkephalin

92
Q

How does one become tolerant of opioids?

A

Opioid receptors are down-regulated
Molecular uncoupling disrupts OR signals

93
Q

What are pharmacokinetic changes?

A

Changes in distribution or metabolism

94
Q

What are pharmacodynamic changes?

A

Changes in receptor expression, neuroplasticity
Cellular

95
Q

What is learned tolerance?

A

Behaving sober when intoxicated

96
Q

What symptoms of opioid use subside over time?

A

Vomiting, euphoria, respiratory depression

97
Q

What symptoms of opioid use do not subside over time?

A

Constipation and pupil constriction

98
Q

Where might an individual have a lower tolerance to opioids?

A

Different/strange locations and isolation

99
Q

What are common techniques to measure tolerance in rats?

A

Drug treatment regimen to induce tolerance
Tail immersion test
Hot plate test

100
Q

What is used to gauge psychological addiction?

A

Behavioural sensitization
Escalating behavioural responses to a stimulus like a drug of abuse after a drug-free period

101
Q

What are the factors that contribute to sensitization?

A

Receptor density
NT levels
Cell signalling deregulation

102
Q

What is behavioural sensitization is driven by?

A

NAc inputs
Driven by DA-ergic and Glu-ergic projections from the VTA nad PFC to the NAc

103
Q

Blocking what impairs sensitization in rats?

A

D1 in the NAc

104
Q

What does morphine sensitization coincide with?

A

Elevated D1 expression in NAc shell plus elevated ERK1/2 MAPK activity

105
Q

What do AMPA/NMDAR antagonists do?

A

Block the induction of sensitization but not the expression of it

106
Q

What are some characteristics of opioid desensitization?

A

Rapid
Direct consequence of drug-receptor activation D
Depends on Ca and K activities
Sustained desensitization reduces acute effects but enhances intracellular signaling

107
Q

What are some mechanisms of opioid desensitization?

A

G-protein uncoupling, alpha-GTP binding is reduced in morphine-treated animal

gRK phosphorylation of MOR causes beta-arrestin binding and reduced euphoria/analgesia

108
Q

What are the symptoms of heroin withdrawal 6 hours after last dose?

A

Craving, anxiety

109
Q

What are the symptoms of heroin withdrawal 612-14 hours after last dose?

A

Yawning, sweating, watery eyes, runny nose

110
Q

What are the symptoms of heroin withdrawal 614-16 hours after last dose?

A

Pupils dilate, goose bumps, hot/cold flashes, fever, diarrhea, aching, no appetite

111
Q

What are the symptoms of heroin withdrawal 2-5 days after last dose?

A

Weakness, depression, insomnia, elevated BP/HR/respiration, restlessness, hyperglycemia

112
Q

When do heroin withdrawal symptoms subside?

A

By the 5th day

113
Q

What acute effects of heroin is rapid tolerance developed?

A

Euphoria, analgesia, respiratory, vomiting effects

114
Q

What acute effects of heroin is slow tolerance developed?

A

Itching
Urinary retention

115
Q

What contributes to the affective signs of withdrawal?

A

The mesolimbic system

116
Q

What does naloxone injection to NAc do?

A

Cause conditioned place aversion

117
Q

What do D2-like receptor agonists injected into the NAc do?

A

Reduces somatic withdrawal signs

118
Q

What is decreased in the NAc during withdrawal?

A

DA

119
Q

What are the affective symptoms of opioid withdrawal?

A

Dysphoria
Anxiety
Irritability
Cravings

120
Q

What symptoms of opioid withdrawal are important targets for therapy and why?

A

Affective symptoms to prevent relapse

121
Q

How long can anxiety due to opioid withdrawal last?

A

Up to 80 days

122
Q

How long do conditioned place aversions last?

A

20 days

123
Q

What opioid receptors are present in the LC?

A

MOR and KOR

124
Q

What does chronic opioid use do to the LC?

A

Suppressed LC activity
Less noradrenaline is released

125
Q

How does LC normalize activity in the presence of opioids?

A

Tolerance

126
Q

What happens to the LC when we remove opioids?

A

It becomes overactive
Causes noradrenaline surge

127
Q

What opioid withdrawal symptoms does the LC contribute to?

A

Sweating
Chills
Stomach cramps
Emesis
Diarrhea
Muscle pain
Runny nose and eyes

128
Q

Where is the paragigantocellularis (LPGi) located?

A

In the rostroventral medulla (RVM)

129
Q

What does the LPGi do?

A

Stimulates LC via glu-ergic inputs
Modulates opioid withdrawal symptoms

130
Q

What does adolescent opioid exposure do?

A

Alters longterm activity in brainstem regions and increases severity of adult withdrawal symptoms

131
Q

What are clonidine and lofexidine?

A

Alpha2-adrenoceptor agonists

132
Q

How does clonidine and lofexidine treat opioid withdrawal?

A

Prevents noradrenaline release via pre-synaptic alpha2 autoreceptors
Targets the LC and its projections

133
Q

What is buprenorphine?

A

Semi-synthetic partial agonist

134
Q

How does buprenorphine treat opioid withdrawal?

A

Used for maintenance
Outcompetes morphine and blocks heroin with mild effects
Taken orally, 37 hour half-life, safer

135
Q

What happens if a user tries to inject buprenorphine?

A

Contains suboxone = 4:1 buprenorphine-to-naloxone sublingual
The effects are blocked if injected because naloxone does not cross the mucosal membrane

136
Q

What is methadone?

A

NMDAR antagonist

137
Q

How does methadone treat opioid withdrawal?

A

Used for maintenance
Long half-life
No adulterants
Mild euphoria, causes constipation

138
Q

Why are adulterants put in street drugs?

A

To increase bulk or modulate/enhance rushes

139
Q

What are the features of talcum powder and powdered milk as an adulterant?

A

Inert, increases mass, decreases purity

140
Q

What are the effects of quinidine/quinine as an adulterant in opioids?

A

Bitter taste mimics heroin
Hypotensive effect feels like a heroin rush

141
Q

What are the dangers of fentanyl and carfentanil as adulterants in opioids?

A

Fentanyl is found ing >50% of street opioids and is 100x more potent than morphine
Carfentanil is 10000x more potent than morphine

142
Q

What is the main mechanism of depressed respiration in opioid overdose?

A

Reduce pre-Botzinger complex output

143
Q

What is the role of the RTN/pFRG?

A

Coupled oscillator that influences motoneurons that produce breathing

144
Q

What factors contribute to depressed respiration in opioid overdose?

A

Unresponsiveness
Upper airwar obstruction due to reduced upper airway muscle tone = genioglossus
Central respiratory depression = Pre-BotC effects

145
Q

What is the opioid triad?

A

Coma, depressed respiration, pinpoint pupils

146
Q

What receptors does naloxone target?

A

MOR, KOR, DOR

147
Q

What is the mechanism of naloxone?

A

Competitive antagonist at opioid receptors
Short-acting due to metabolism