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PHYL2064 > Pharmacology L5: Opioid > Flashcards

Pharmacology L5: Opioid Flashcards

1
Q

Opioid causes number of changes in the _____ ability to function

A

neurons

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2
Q

Opioids might close _____ channels. What does that do?

A

calcium

Reduce transmission (Reducing the neurons ability to transmit pain signals to the brain)

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3
Q

Opioids might open _____ channels. What does that do?

A

potassium

Hyperpolarizes (less likely to fire- less excitable)

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4
Q

What are 5 agonists of opioids?

EXAM QUESTION

A
  1. morphine
  2. codeine
  3. heroin
  4. hydrocodone
  5. buprenorphine
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5
Q

What are 2 antagonists of opioids?

EXAM QUESTION

A
  1. naloxone
  2. naltrexone.

Antagonist –> important for treating overdose

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6
Q

What is nociception?

A

the physiological ability to sense pain, as encoded by nociceptor stimulation

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7
Q

What is the purpose of anatgonists for opioids?

A

Important for treating overdose

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8
Q

What does pain management look like?

A
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9
Q

What is the pain management if the pain rating is 1-3/10?

A

Non-opioid (NSAIDS)

Non-pharmacological +/- adjuvants

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10
Q

What is the pain management if the pain rating is 4-6/10?

A

Non-opioids + weak opioid combination

Non-pharmacological +/- adjuvants

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11
Q

What is the pain management if the pain rating is 7-10/10?

A

Strong opioid +/- adjuvants

Non-pharmacological

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12
Q

When are strong opioid +/- adjuvants used?

A

Eg. End stage cancer, chronic pain

Usually in hospital

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13
Q

What are the 4 major adverse effects of opioids?

A
  1. Constipation
  2. Nausea and vomiting
  3. Sedation
  4. Respiratory depression
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14
Q

Why is it important to monitor to prevent and/or intervene for opiods?

A

Due to the major adverse effects

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15
Q

What happens in pain from stimulus (heat/cold/pressure- tissue injury) and to the sensation of pain?

A

Tissue injury –> Histamine ..etc can trigger nociceptive neuron to trigger an AP –> goes to spinal cord –> synapses in dorsal horn –> nociceptive signals are sent from spinothalamic tract –> CNS –> processing in thalamus and somatosensory cortex –> pain is experiences

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16
Q

____ and ____ cells dump histamine

A

Neutrophils; mast

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17
Q

What does histamine?

A

Histamine can activate/irritate

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18
Q

What are the 6 indicators of tissue damage?

A
  1. Histamine
  2. Bradykinin
  3. 5-HT
  4. Prostaglandins
  5. ATP
  6. Acid (H+)
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19
Q

What is pain?

A

Pain is an emotional reaction to nociceptor activation (experiences can be different; pain thresholds)

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20
Q

What is the descending inhibitory pathway?

A

Signals can be sent to try a reduce pain naturally

This pathway is key to the body’s endogenous pain management system, which utilises 5-HT (serotonin) and enkephalins, the latter of which blocks spinothalamic transmission of pain.

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21
Q

What is the purpose of descending inhibitory pathway?

A

This pathway is key to the body’s endogenous pain management system, which utilises 5-HT (serotonin) and enkephalins, the latter of which blocks spinothalamic transmission of pain.

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22
Q

What are 3 structures that are related in descending inhibitory pathway?

A
  1. Periaqueductal grey (PAG)
  2. Rostral ventromedial medula (RVM)
  3. Substantia gelantinosa
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23
Q

How do the 3 structures related to the descending inhibitory pathway?

A
  1. Cortical brain regions project downwards to the periaqueductal grey (PAG) region of the midbrain.
  2. The PAG neurons project to the rostral ventromedial medulla (RVM) and then onwards to the dorsolateral funiculus in the spinal cord.
  3. Both substantia gelatinosa (afferent) and PAG (descending inhibitory) are rich in opioid receptors, and as opioids reduce activity in afferent and promotes activity of the descending inhibitory pathway, nociception and pain are reduced.- Waiting to be activated by natural opioid receptors or opioid medication
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24
Q

Morphine and codeine have been used for centuries as powerful _____, for _____, and to relieve diarrhoea, identification of receptors for these compounds was confounding.

A

analgesics; euphoria

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25
Q

How is morphine made? How is heroin made?

A

Poppy plant –> extracted –> morphine –> can be changed into heroin

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26
Q

Scientists began to search for _____ compounds with affinity for these receptors, leading to the discovery of neuropeptides including _____, _____ and _____, which comprise the endogenous analgesia system.

A

endogenous;

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27
Q

What are enkephalins, endorphins, and dynorphins?

A

Peptides which the brain can manufacture to help with pain relief = endogenous analgesia

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28
Q

How do peptides (enkephalins, endorphins, and dynorphins) work?

A
  • These natural peptides are generated from a precursor proteins.
  • These are then enzymatically cleaved and modified posttranslationally.
  • Not all cells do this equally, and processing is a result of demands on the cell.
  • These can differentially impact the receptors in the pain pathway. Synthesized in long strands
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29
Q

How does morphine work as a natural peptide?

A

Also binds to opioid receptors just as endogenous compounds do = activates = reduce pain sensation

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30
Q

How does naloxone work as natural peptide?

A

Blocks receptors from binding= Prevent morphine from activating

  • Used to manage overdose
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31
Q

What are opiates?

A

alkaloids structurally related to opium poppy plant products, e.g. morphine and codeine.

These do not have peptide structures! Natural

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32
Q

What are opioids?

A

any compound that has functional and pharmacological properties of an opiate,

e.g. methadone, fentanyl, buprenorphine), plus neuropeptides, which bind to opioid receptors, produce morphine-like effects, and are blocked by antagonists such as naloxone. Natural and chemically made

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33
Q

Opioids are _____ (hydro/lipo)philic.

A

lipophilic

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34
Q

Morphine and codeine are made from _____

A

plant

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35
Q

_____ has the orange region which is structurally similar to our own endogenous system

A

Morphine

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36
Q

_____ binds but doesn’t have an effect

A

Naloxone

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37
Q

Why is heroin so dangerous?

A

Heroine can pass blood brain barrier quickly because it is lipophilic = faster and high concentration

  • Made synthetically

Taken -OH on morphine and place them with groups that is more lipophilic

Heroin is modification of morphine, with its hydroxyl groups made even more lipophillic for better BBB effects.

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38
Q

Morphine is relatively ____(hydro/lipo)philic so less morphine crosses into the CNS than the more ____(hydro/lipo)phillic opioids.

A

hydro; lipo

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39
Q

Which receptor subtypes have been identified?

A
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40
Q

What are the 2 endogenous agonists of mu as an opioid receptor?

A
  1. Endorphins
  2. enkephlins
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41
Q

What are the 2 endogenous agonists of delta as an opioid receptor?

A
  1. Endorphins
  2. enkephlins
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42
Q

What are the 3 endogenous agonists of kappa as an opioid receptor?

A
  1. Dynorphins A
  2. Dynorphins B
  3. neoendorphin
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43
Q

What was mu (opioid receptor) nameed for?

A

morphine

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44
Q

What was delta (opioid receptor) nameed for?

A

vas deferens tissue

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45
Q

What was kappa (opioid receptor) nameed for?

A

ketocyclazocine

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46
Q

What are the 3 opioid receptors?

A
  1. μ, mu, MOPr
  2. d, delta, DOPr
  3. k, kappa, KOPr
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47
Q

Each of these receptors is activated by some or all of the _______. Receptors are located throughout the CNS, but particularly in the tracts and areas associated with nociception.

A

endogenous opioids

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48
Q

What is the mechanism of action of opioids?

A

The net outcome is inhibitory synaptic function of neurons with opioid receptors, usually reducing release of glutamate as neurotransmitter within the spinal column.

  • GCPR Cascade associated with it G protein when activated
  • Inhibitions action
  • Promotes potassium efflux
  • Causes hyperpolarization
  • Reducing the ability of the neuron to respond to the release of neurotransmitters
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49
Q

What is the spatial mechanism action of opioid receptors?

A

More than 75% of opioid receptors in the dorsal horn of the spinal cord are located presynaptically and most are μ receptors.

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50
Q

What are the 2 activation of opioid receptors?

A
  1. inhibits presynaptic Ca2+ ion channel opening (decreasing neurotransmitter release)
  2. opens postsynaptic K+ ion channels (causing hyperpolarization/IPSP)

This leads to reduced synaptic activity in neuronal circuits containing opioid receptors.

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51
Q

What does spatial mechanism of opioid receptors look like?

A

In Dorsal horn

Pre-synaptically; mostly mu

Opioid receptor (eg. mu) –> inhibit Ca2+ –> inhibit release of neurotransmitter –> efflux of K+ –> less responsivness post-synaptically

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52
Q

What are 3 ways of pain relief?

A
  1. Nociceptors
    • Opioids acts peripherally to decrease excitability of sensory nerves, reduces Substance P (SP) release, decreasing pain transmission.
  2. Spinal Cord (ascending)
    • Opioids prevent pain transmission by binding presynaptic μ receptors, decreasing calcium influx and preventing vesicle release, especially glutamate
    • Opioids binds postsynaptic μ receptors, increasing K+ influx and hyperpolarizes post-synaptic neurons in periaqueductal gray (PAG).
  3. Descending Pathway
    • activates μ receptors on descending GABA-releasing neurons in PAG in the midbrain, inhibiting them and inducing NE and 5-HT-production of pain inhibitory neurons. This leads to spinal block of pain.
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53
Q

How does NSAIDS work as pain relief?

A

Peripheral level

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54
Q

What are 2 ways pain relief can occur in opiates?

A

Activation and stimulation of pain fibres

  1. Slow down transmission of pain
  2. Stimulate the descending inhibitory pathway –> increase serotonin and noradrenaline –> relieve pain
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55
Q

What are the 3 key pain relief ways?

A
  1. Activation and stimulation of pain fibres
  2. Slow down transmission of pain
  3. Stimulate the descending inhibitory pathway –> increase serotonin and noradrenaline –> relieve pain
56
Q

What are the major pharmacologic effects of opioid agonists? EXAM QUESTION

A
57
Q

What is Dysphoria?

A

extreme lack of joy

58
Q

What is Euphoria?

A

extreme joy

59
Q

Why is codeine used for coughs?

A

Inhibition of the cough reflex is why we used codeine

60
Q

What is miosis?

A

pin points pupils

61
Q

What are the most common opioid receptors?

A

Mu receptors

62
Q

What are the 7 CNS effects of opioid agonists?

EXAM QUESTION

A
  1. Analgesia
  2. Dysphoria or euphoria
  3. Inhibition of cough reflex
  4. Miosis Physical dependence
  5. Respiratory depression
  6. Sedation
63
Q

What are 2 cardiovascular effects of opioid agonists?

EXAM QUESTION

A
  1. Decreased myocardial oxygen demand
  2. Vasodilation and hypotension
64
Q

What are the 2 gastrointestinal and biliary effects of opioid agonists?

EXAM QUESTION

A
  1. Constipation (increased intestinal smooth muscle tone)
  2. Nausea and vomiting (via CNS action)
65
Q

What are the 3 effects of opioid agonists? How does that work?

EXAM QUESTION

A
  1. flushing
  2. pruritus itching
  3. Hives or other rash

Mast cell release of histamine

66
Q

Standard doses of opioids for pain relief do not significantly reduce ____ rates.

A

breathing

67
Q

What is respiratory depression as a result of opioid?

A
  • However, respiratory depression is the primary cause contributing to death with opiate therapy, due to arrest or obstruction.
  • Respiratory tidal volume decreases, and breathing rate decreases to 3-4 breaths per minute with overdose/abuse.
68
Q

What are 2 symptoms of decreased respiratory tidal volume due to opioid?

A

Decreased tidal volume

  1. Blueness
  2. Pin point pupils
69
Q

Why is heroin dangerous to the body and how does the body OD?

A

Eg. heroin (illegal not pure and not sure what % is in drug –> body may be aclimated to 5-% pure but buy 90%) –> can cause body to OD)

70
Q

Opioids reduces normal stimulation of respiratory centres by _____ CO2 levels, and also increases chest wall rigidity.

A

increased

Opioids blocks reflex –> when CO2 concentration increases = breathing rate increases (to clear that)

71
Q

What are the respiratory effects of opioids?

A

These respiratory effects are quickly reversed with administration of antagonist, e.g naloxone, with μ receptors are the key agents in this side effect.

72
Q

What is miosis?

A
  • Miosis is an important diagnostic indicator of opioid overdose. There is little to no tolerance to this effect, so it can be useful in diagnosis of opioid overdose.
  • Pupil constriction is due to direct stimulation of the Edinger- Westphal nucleus of cranial nerve III, which activates the parasympathetic innervation of the iris sphincter muscle.
73
Q

What are the cough suppression effects?

A

Cough suppression effects do not easily correlate with analgesia or respiratory effects; for this goal, codeine is used at sub-analgesic concentrations.

74
Q

What are the 2 opioid effects on gastrointestinal system?

A
  1. Constipation due to increase in tone and decrease in motility:
    • Delay of passage of food (gastric contents) which may lead to increased retention of water.
    • Tolerance does not develop (same effect each time) to this constipation effect.
  • Nausea and vomiting are reported in ~45% of patients, but tolerance develops with repeated use – action via chemoreceptor trigger zone.
75
Q

What are the 2 characteristics of constipation due to increase in tone and decrease in motility?

A
  1. Delay of passage of food (gastric contents) which may lead to increased retention of water.
  2. Tolerance does not develop (same effect each time) to this constipation effect.
76
Q

What is nausea and vomiting?

A

Nausea and vomiting are reported in ~45% of patients, but tolerance develops with repeated use – action via chemoreceptor trigger zone.

77
Q

What is morphine metabolism?

A
  • Morphine is well-absorbed in the gut, and undergoes extensive first-pass metabolism in the liver.
  • Most is converted to glucuronides in urine.
  • Morphine-3-glucuronide is the main product, and it is pharmacologically not active.
  • Morphine-6-glucuronide, however, has more analgesic activity than morphine, with a longer half-life as well – can accumulate. Hepatic disease may impact on metabolism.
78
Q

What is codeine metabolism?

A
  • Sue less dosage than analgesia –> not as effective compare to morphine
  • Codeine: undergoes less first-pass metabolism than morphine, so has greater bioavailability.
  • Codeine is converted to morphine by CYP2D6, which has significant genetic variation.
  • Mothers who are rapid metabolizers of codeine may expose their foetus or nursing infant to a morphine overdose. Sue less dosage than analgesia –> not as effective compare to morphine
79
Q

What are stimulant and dampening effects of opioids?

A
80
Q

Strong or moderate agonists, usually high affinity for ____ receptors, and lower affinity for ___ and ___.

A

μ; d; k

81
Q

Strong agonists in humans are _____ when given in a dosage sufficient to relieve severe pain.

A

well tolerated

Won’t have side effects (in short term)

82
Q

Moderate agonists will cause _____ side effects if given in doses sufficient to relieve severe pain. How are they used?

A

intolerable (eg. need to give more as not strong enough and then can cause side effects)

Lower concentrations of moderate agonists are often coupled with NSAIDs for pain treatment.

83
Q

How are moderate opioids used?

A

Use moderate opioids combined with NSAIDS

  • Eg. ibuprofen and codeine = neurofen plus
  • Both involved in pain relief
  • Dose of both individually is not dangerous
  • When combined –> strong enough pain relief
84
Q

What are the mild, moderate and strong agonists?

A
85
Q

What is used for opioid overdose?

A

Opioid antagonists (naloxone and naltrexone) are given to treat overdose.

86
Q

What is the gold standard?

A

Morphine

87
Q

What is morphine as an agonist?

A

Morphine is actually a partial agonist on μ opioid receptors;

88
Q

What are 4 characteristics of morphine?

A
  1. Morphine is actually a partial agonist on μ opioid receptors
  2. MOA and effects have been covered previously.
  3. Used for severe pain treatment.
  4. Promote potassium ion efflux or prevents calcium ion influx to prevent the depolarisation
89
Q

What is Fentanyl?

A

synthetic strong opioid agonist

90
Q

Fentanyl has been formulated into a patch to provide continuous pain relief for patients with severe or chronic pain. This delivery system is possible due to its ____ (high/low) potency and ____ solubility.

A

high; lipid

Can be transmitted through skin into blood = high lipophilic

91
Q

When is fentanyl used?

A

Not in hospital or cognitively unable to manage/remember medication

92
Q

Fentanyl is often used in ______ conditions, and can be used to bring down large mammals (a.k.a. large elephants) due to faster onset than morphine.

A

general anaesthetic

IV drip

Quite a strong sedative

Used medicinally

93
Q

What is Methadone?

A

strong long-acting synthetic agonist

94
Q

What are 3 characteristics of Methadone?

A
  1. Can be given just once a day in a controlled environment to control withdrawal. Addicts to heroin may be placed on a methadone maintenance program.
  2. Used to treat opioid/heroin addiction or chronic pain. Does not cause euphoric effects; can reduce criminal behaviour, reduce needle sharing and transmission of HIV and hepatitis B or C.
  3. Methadone can be lethal in overdose, if injected, or when combined with other drugs such as alcohol and minor tranquilisers (benzodiazepines).
95
Q

How does Methadone work as treatment for Methadone?

A

Can buy time –> prevent euphoria –> start reducing doses

96
Q

How can methadone be lethal?

A

overdose, if injected, or when combined with other drugs such as alcohol and minor tranquilisers (benzodiazepines).

97
Q

What are 2 situations where there is highest mortality with morphine?

A
  1. OD on heroin
  2. Combining heroin with alcohol
98
Q

What happens when heroin (opioid) is combined with alcohol?

A
  • When heroin (opioid) is combined with alcohol
  • Potential to depress CNS
    • Opioid receptor –> heroin
    • GABA-A –> alcohol
  • When combined –> combined suppression of CNS activity = heightened respiratory depression
99
Q

What does the Hydrocodone (Vicodin): semi synthetic - moderate?

A
100
Q

What is Pethidine?

A

synthetic moderate

101
Q

What does Pethidine tend to cause?

A

Tends to cause restlessness, euphoria, and has antimuscarinic effects as well; but no miosis.

Moderate –> so not for severe pain

102
Q

When is Pethidine preferred over Morphine?

A

Preferred to morphine during labour as it does not affect uterine smooth muscle function.(won’t reduce contractions)

103
Q

Why is morphine not suitable for labour?

A

Morphine may slow down the contractility of the uterus (as well as GIT)

104
Q

What is Buprenorphine?

A

A μ-opioid partial agonist that suppressed withdrawal and cravings.

105
Q

What is the ceiling effect of Buprenorphine?

A

Ceiling effect exists for respiratory depression, in which higher doses of buprenorphine cause no additional effects.

106
Q

How is Buprenorphine co-packaged?

A

Buprenophine and naloxone = co-packaged

  • Naloxone is the antagonist
  • Buprenophine is a partial agonist
107
Q

How is Buprenorphine given?

A

Tablet given sublingually –> absorbed in the vasculature under the tongue

  • Buprenophine = absorbed well
  • Naloxone = not absorbed well Not 100% efficacy

Buprenophine is used in patients as a sublingual tablet Interestingly, buprenorphine has been combined with naloxone in a 4:1 ratio (Suboxone), to alleviate worry that the sublingual tablet would be dissolved or injected by addicts.

  • Naloxone is poorly absorbed sublingually and orally, but well absorbed when injected i.v..
  • This means that a user injecting
  • Suboxone would experience withdrawal symptoms due to naloxone occupying mu receptors.
108
Q

Why should you not inject suboxone?

A

Used injecting suboxone would experience withdrawal symptoms due to naloxone occupying mu receptors and prevent the opioid from occupying the receptor

109
Q

Why is buprenorphine safer as addicts?

A

are less likely to overdose

Ceiling effect exists for respiratory depression, in which higher doses of buprenorphine cause no additional effects.

110
Q

What are the 2 characteristics of Moderate opioid agonists for moderate pain?

A
  1. As the concentrations used of these agents is lower than that needed for complete analgesia, they are combined with either paracetamol, aspirin, or ibuprofen.
  2. Codeine does produce significant antitussive effects, and as such, may be included in cough mixtures to prevent coughing.
111
Q

What is Panadeine?

A

Paracetamol + codeine (co-package)

112
Q

What is Nurofen Plus?

A

Ibuprofen + codeine (co-packaged)

113
Q

As the concentrations used of these agents is ___ (higher/lower) than that needed for complete analgesia, they are combined with either paracetamol, aspirin, or ibuprofen.

A

lower

114
Q

____ does produce significant antitussive effects, and as such, may be included in cough mixtures to prevent coughing.

A

Codeine

115
Q

What are 2 antagonists of opioids?

A

naloxone and naltrexone

116
Q

What is the purpose of antagonists of opioids?

A

These compounds prevent or abolish excessive respiratory depression caused by the morphine or related compounds.

117
Q

How do opioid antagonists work?

A

They are pharmacological antagonists, competing for opioid receptor binding sites.

Their structures are related to morphine.

118
Q

How does Naloxone work?

A

Naloxone is a pure antagonist with no morphine like effects.

It blocks the euphoric effect of heroin when given before heroin, and is short acting.

119
Q

How does Naltrexone work?

A

Naltrexone’s actions resemble those of naloxone, but naltrexone is well absorbed orally and is long acting, making it useful in narcotic treatment.

120
Q

What is an overdose?

A

an excessive and dangerous dose of a drug, can mild, moderate, severe or lethal.

121
Q

Most people who overdose are under the influence of _____ drug – on average 2.7 drugs are identified in fatal overdose cases.

A

more than one

122
Q

When overdose is lethal, it is common that no single drug is present at a lethal dose. Rather it is the _____ effects of _____ the drugs that is lethal.

A

synergistic; combining

123
Q

The majority of overdoses involve ____ drugs.

A

legal

124
Q

A combination of _____ (heroin or prescription painkillers) and _____ can be especially dangerous. Both suppress breathing, but by different mechanisms.

A

opiates; alcohol

125
Q

How does opiate cause respiratory failure and as a result death?

A

Prescription opioids are the cause for more deaths by overdose than any other single drug.

  • Alcohol overdose can also suppress breathing by either decreasing the excitatory effect of glutamate, such that high doses can result in passing out and reduced breathing; and/or an unconscious individual may inhale their own vomit, which then further reduces breathing.
126
Q

What is the classic example of how receptor desensitization/down-regulation is important clinically?

A
127
Q

Case study:

  1. 52 yr man with multiple myeloma-> standard chemotherapy. Needed pain relief.
  2. Commenced morphine 10 mg orally every 4 hr. Major side effect was constipation (treated with laxatives). Respiratory rate normal.
  3. After several months, required increased dose of 120 mg daily.
  4. After 12 months dose increased to 300 mg daily.
  5. Maintained for 3 months, then -> 800 mg daily -> 1,000 mg daily.
  6. Final respiratory rate = 8 per minute (normal) – normal blood gases.

How does the body accept that? How does the normal person respond?

A

Pain was well managed

Body adapts = downregulated and de-sensitised opioid receptors = high concentrations are now needed to activate them

  • Eg. ordinary person given 1000mg of morphine daily = severe effects
128
Q

Case study:

  1. 52 yr man with multiple myeloma-> standard chemotherapy. Needed pain relief.
  2. Commenced morphine 10 mg orally every 4 hr. Major side effect was constipation (treated with laxatives). Respiratory rate normal.
  3. After several months, required increased dose of 120 mg daily.
  4. After 12 months dose increased to 300 mg daily.
  5. Maintained for 3 months, then -> 800 mg daily -> 1,000 mg daily.
  6. Final respiratory rate = 8 per minute (normal) – normal blood gases.

Why did respiratory depression not occur?

A

Tolerance increased

129
Q

Does Miosis occur after opioid?

A

Miosis would occur as tolerance does not occur for this

130
Q

Morphine and codeine are both found in the poppy plant pods. (True/False)

A

True

131
Q

Morphine and heroin are both found in the poppy plant pods. (True/False)

A
  1. False –> heroine is synthesized (illegal illicit)
132
Q

The most common opioid receptors in the CNS are mu receptors. (True/False)

A
  1. True –> mu = morphine
133
Q

Activation of mu receptors leads to respiratory depression and pin-point pupils. (True/False)

A

Yes if used at high conc. For long periods of time • If taken properly (over the counter/by prescription) = okay

134
Q

Codeine is useful in cold medication as an antitussive compound. (True/False)

A

True

135
Q

Morphine is metabolised in the liver to inactive compounds. (True/False)

A

True

136
Q

In case of overdose, ____________ is the antagonist for mu receptors.

A

Yes if used at high conc. For long periods of time • If taken properly (over the counter/by prescription) = okay

137
Q

Explain the difference between strong and moderate opioid agonists, and their plausible use in pain relief. (True/False)

A

Moderate opioids get co-packaged to ensure that don’t become addicted and allows pain relief to be strong enough ○ Individually not strong enough Combined = strong enough

PHYL2064 (29 decks)

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