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Pharmacology > Week 9 Opioid Analgesic Drugs > Flashcards

Week 9 Opioid Analgesic Drugs Flashcards

1
Q

a-delta fibers (nociceptors) mediate what kind of pain?

A

somatic

small, myelinated, sharp & localized pain

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2
Q

c-fibers mediate what kind of pain?

A

visceral

small than a-delta; unmyelinated, dull/diffuse/aching/burning pain

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3
Q

afferent fibres release which NTs to stimulate the ascending spinothalamic pathway?

A

substance P

glutamate

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4
Q

descending pain-inhibitory tracts release what substances to decrease pain perception?

A

serotonin
norepinephrine
enkephalin

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5
Q

define analgesia / analgesics

A

absence of pain without losing consciousness

state in which no pain is felt despite presence of normally painful stimuli

analgesics alleviate pain without major impairment of other sensory modalities

  • opioid analgesics
  • non-opioid analgesics
  • disease-specific analgesics
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6
Q

what 3 major areas in the CNS mediate the analgesia system?

A
  • periaquaductal grey matter (in midbrain)
  • nucleus raphe magnus (in medulla)
  • pain inhibitory neutrons within dorsal horns of spinal cord (act to inhibit pain-transmitting neurons also located in spinal dorsal horn)

these areas are where chemical mechanisms of opioid analgesics will take place

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7
Q

opioids used to be called?

A

narcotics

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8
Q

what are the 2 subgroups of opioid analgesics? & which is most commonly used?

A 
Mu agonist (morphine-like) - m/c
agonist-antagonist
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9
Q

give 3 examples of Mu agonist opioids

A 
morphine
oxycodone (percocet/oxycontin)
codeine (tylenol 3)
hydrocodone (vicodin)
hydromorphone
meperidine (demerol)
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10
Q

describe ‘opioid’

A

natural or synthetic drug that binds to opioid receptors producing agonist effects

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11
Q

where are the 2 places natural opioids come from?

A 
papaver somniferum (opium poppy)
as endogenous endorphins

all others prepared from either:

  • morphine (e.g. heroin)
  • synthesized from precursor compounds (e.g. fentanyl)
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12
Q

3 major families of opioid peptides

A

enkephalins (delta)
endorphins (mu)
dynorphins (kappa)

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13
Q

where are opioid receptors primarily found?

A

CNS (limbic system [euphoria]; thalamus & substantia gelatinosa [dull pain relief]; brain stem [pupil constriction, resp depression]; Large intestine [constipation])

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14
Q

what happens during opioid receptor activation?

A

at PRE-SYNAPTIC receptors:
- decreased synthesis of cAMP, which decreases Ca2+ influx & thus inhibits release of excitatory NTs (glutamate, subP)

at POSTSYNAPTIC level:
- increased K+ conductance (hyper polarize cell) K+ moves out of cell – decreases probability of generation of action potential

therefore: decreased neuronal transmission (glutamate, Ach, NE, 5-HT, subP)

essentially turn off the neuron & thereby block relaying of pain signals from nociceptors

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15
Q

where is Mu-1 receptor & what is it responsible for?

A

located outside spinal cord

responsible for central interpretation of pain

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16
Q

where is Mu-2 receptor & what is it responsible for?

A

located throughout CNS

responsible for respiratory depression, spinal analgesia, physical dependence, euphoria

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17
Q

what is considered the deadly side effect of opioid analgesic drugs?
(cause of death in all overdose cases)
which receptor is responsible for this response?

A

respiratory depression

Mu-2 receptors

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18
Q

differentiate mu & kappa receptors

A

kappa receptors:

  • assoc. directly w analgesia & sedation
  • no undesired side effects as seen w mu receptors
  • kappa receptors only affect nerves that relay pain produced by non-thermal stimuli

mu receptors:

  • inhibit all pain signals
  • undesired side effects such as respiratory depression, decreased GI motility, physical dependence
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19
Q

delta receptor is strongest binding site of which class of opioid peptides

A

enkephalins

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20
Q

what is the ORL-1 receptor

A

“orphan” receptor
most recently discovered
opioid peptide ligand for this receptor: nociceptin

ORL-1 associated w many different effects e.g. memory, CV function, renal function

may have effects on dopamine levels; assoc. w NT release during anxiety

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21
Q

principal uses of opioids?

A
  • relief of most types of moderate-to-severe visceral or somatic pain
  • symptomatic treatment of acute diarrhea
  • cough suppression
  • tx of opiate addiction & alcoholism
  • anesthetic adjunct
  • reversal of opioid overdose by opioid-receptor antagonists
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22
Q

which opioid drugs are strong, full agonists?

affinity for binding + efficacy

A

morphine, methadone, fentanyl

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23
Q

which opioid drugs are moderate, full agonists?

A

codeine, oxycodone

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24
Q

which opioid is a partial/mixed agonist-antagonist?

produces agonist effect at one receptor & antagonist effect at another

A

pentazocine

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25
Q

which opioid is an antagonist?

affinity for binding but no efficacy; blocks action of endogenous & exogenous ligands

A

naloxone, naltrexone

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26
Q

absorption of opioid drugs

A
  • well absorbed via GIT ; often given parenterally

- IM injections no longer recommended

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27
Q 
time (latency) to onset:
oral
intranasal
IV
pulmonary-inhalation
A

oral: 15-30 mins
intranasal: 2-3 minutes
IV: 15-30 seconds
pulmonary-inhalation: 6-12 seconds

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28
Q

which 2 opioids have active metabolites after phase I detox?

A

morphine

codeine

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29
Q

opioid elimination primarily via?

A

kidney

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30
Q

CIs for opioid use?

A 
increased intracranial pressure
decreased ventilation (COPD, cor pulmonale, emphysema, asthma)
hx opiate addiction/allergy
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31
Q

precautions in dosing opioids needed in these 5 cases

A 
elderly
debilitated
under 18 yrs of age
renal/hepatic disease
opioid naive (not been taking opioids regularly)
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32
Q

Opioids are unique amongst analgesics in that they are able to increase the pain tolerance by blunting the _________ response (even when no change in pain threshold to stimuli)

A

LIMBIC (emotional)

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33
Q

what kind of pain are opioids most effective in relieving?

A

dull, diffuse, continuous pain

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34
Q

Opiates suppress the “_____ center” which is also located in the brainstem, the medulla.
esp. which drug?

A

cough center

esp. codeine

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35
Q

how do opioids cause constipation?

A
  • delays gastric emptying
  • causes spasmodic increases in intestinal smooth muscle tone
  • reduces intestinal secretions
  • increases anal sphincter tone
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36
Q

most serious side effect of opioids?

A

respiratory depression

principal cause of death

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37
Q

9 adverse effects of opioids?

A 
respiratory depression
constipation
nausea
endocrine effects
miosis (papillary constriction)
euphoria
itchiness (increased histamine release)
tolerance
physical dependence
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38
Q

what are adverse effects on endocrine system?

A 
inhibits GRH (lowers LH, T)
inhibits release of antidiuretic hormone
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39
Q

tolerance develops to which side effects of opioids?

A

respiratory effects
analgesic effects
euphoric effects
sedative effects

no tolerance to miosis /constipation effects

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40
Q

2 drug interactions and 1 CI?

A

sedative hypnotics - increased CNS depression (esp. resp)
TriCyclicAntidepressants & antipsychotic drugs - increase sedation

CI: MAOI - high incidence of hyperpyrexic coma

41
Q

morphine has high binding affinity for which receptors and less affinity for which 1 receptor?

A

high - mu and delta

weak - kappa

42
Q

how is morphine administered?

A

subcutaneous
intravenous
epidural injections
orally in solution (far less potent)

43
Q

which is faster acting? morphine or codeine?

A

codeine

44
Q

which is faster acting? morphine or heroin?

A

heroin

45
Q

latency to onset of morphine?

A

15-60 mins

46
Q

duration of action of morphine?

A

3-6 hours

47
Q

why does oral dosing of morphine have poor availability?

A

first-pass metabolism

48
Q

how much morphine is protein-bound in blood?

A

30%

49
Q

major pathway for metabolism of morphine (excretion)

A

conjugation with glucoronic acid in the liver to:
morphine-6-glucuronide (very potent analgesic)
morphine-3-glucuronide (no analgesia)

both excreted primarily in urine
small quantities in bile

50
Q

which morphine metabolite is responsible for interactions with opioid receptors?

A

morphine-6-glucoronide

51
Q

latency to onset of hydromorphone?

A

15-30 mins

52
Q

duration of action of hydromorphone?

A

3-4 hours

53
Q

peak effect of hydromorphone felt after how long?

A

30-60 mins

54
Q

hydromorphone is how many times more potent of an analgesic than morphine?

A

7-10 times

55
Q

fentanyl routes of administration?

A

oral
transdermal
possibly IV

56
Q

latency to onset of fentanyl?

A

7-15 mins oral

12-17 hours transdermal

57
Q

duration of action of fentanyl?

A

1-2 hours oral

72 hours transdermal

58
Q

what percentage of fentanyl is protein-bound?

A

80-85%

59
Q

how much of fentanyl is metabolized in liver to inactive metabolites?

A

90%

60
Q

fentanyl is how many times more potent of an analgesic than morphine?

A

80 times!

100micrograms of fentanyl approximately equivalent to 10mg of morphine

61
Q

fentanyl is how many times more potent of an analgesic than hydromorphone?

A

10 times

62
Q

fentanyl has high efficacy for which receptors?

A

mu 1 receptors

63
Q

which opiate is the most effective analgesic?

A

fentanyl

64
Q

codeine is x/6 as strong as morphine

x=?

A

1/6 as strong

65
Q

explain codeine metabolism

A

converted to morphine by 2D6 –> renal elimination

converted to codeine-6-glucoronide 3A4 –> renal elimination

66
Q

what is the more common name of diacetylmorphine?

A

heroin

67
Q

metabolism of heroin

A

heroin (diacetylmorphine) –> 6-monoacetylmorphine –> morphine –> morphine-3-glucoronide or morphine-6-glucoronide

68
Q

heroin binds most strongly to which receptor?

A

mu receptor

69
Q

Heroin produces_________ effects similar to morphine, however, it is thought that these effects are greater and more addicting because of its _____________.

A

euphoric effects

extremely rapid effect.

70
Q

why is heroin so fast-acting?

A

it is extremely lipid-soluble because of its acetyl groups and therefore it immediately crosses the blood brain barrier

71
Q

physiologically, how is a dependence on heroin created?

A

causes body to produce far less endorphins (natural opioid peptides)

72
Q

withdrawal symptoms of heroin

A 
anxiety
depression
cramps
vomiting
diarrhea
restless leg syndrome
severe sense of pain caused by nothing

many addicts in withdrawal experience “itchy blood” which can drive the addict to scratch cuts and bruises into his body

73
Q

what is cross-tolerance & give an example

A

condition where tolerance for one drug produces tolerance for another drug

e.g. someone tolerant to morphine will also be tolerant to analgesic effect of fentanyl, heroin & other opioids

74
Q

why administer methadone in heroin withdrawal?

A

methadone maintenance programs allow heroin users the opportunity to maintain a certain level of functioning without the withdrawal reactions

75
Q

withdrawal reactions are usually the __________ of the physiological effects produced by the drug

A

opposite

76
Q

examples of opioid withdrawal reaction?

A 
pain & irritability
hyperventilation
dysphoria & depression
restlessness & insomnia
hostility
increased blood pressure
diarrhea
pupillary dilation
spontaneous ejaculation
chilliness & "goose flesh"
77
Q

list 3 synthetic opioids

A

hydrocodone (vicodin)
meperidine (demerol)
methadone

78
Q

which opioid analgesic is 10,000 times more potent than morphine and is used as a tranquilizer for large animals?

A

carfentanil

79
Q

vicodin is a solution of which 2 meds?

A

acetaminophen
+
hydrocodone

80
Q

place these in order of weakest to strongest:
vicodin
morphine
codeine

A

codeine –> vicodin –> morphine

81
Q

what is a common side effect of demerol?

A

severe nausea and vomiting

82
Q

why has demerol fallen out of favour in recent years?

A

it has a neurotoxic metabolite

83
Q

percentage-wise, how much of an analgesic effect does demerol have as compared to morphine?

A

10%

84
Q

compare demerol (meperidine) to morphine

A

demerol:

  • does not suppress cough
  • more rapid onset
  • shorter 1/2 life
  • less miosis, constipation & urinary retention
  • equal sedation, euphoria, respiratory depression
  • less histamine release (safer w asthma)
  • tachycardia (vs bradycardia, dry mouth, blurred vision)
85
Q

is methadone addictive?

A

synthesized to not have euphoric properties and mild withdrawal effects
is still addictive.

86
Q

compare methadone, codeine & morphine half lives

A

methadone: 24-48 hours
morphine: 2-4 hours
codeine: 2-4 hours

87
Q

methadone is an analog of which compound?

A

codeine

88
Q

CIs for narcotic analgesics?

A
  • known hypersensitivity
  • acute bronchial asthma, emphysema, upper airway obstruction
  • head injury or increased intracranial pressure
  • convulsive disorders, several renal or hepatic dysfunction, acute ulcerative colitis
89
Q

use narcotic analgesics cautiously with whom?

A
  • elderly patients
  • undiagnosed abdominal pain, liver disease, hx of addiction to opioids, hypoxia, supra ventricular tachycardia, prostatic hypertrophy, renal or hepatic impairment
  • lactation - must wait 4-6 hours after taking the drug before breastfeeding
90
Q

list 2 opioid antagonists

A

naloxone

naltrexone

91
Q

list 3 effects of opioid antagonists

A
  • can reverse effects of mu-opioid agonists
  • can reverse analgesia
  • can cause central opioid withdrawal symptoms in patients who are physically dependent on opioids
92
Q

what are opioid antagonists used to treat?

A

opioid overdose

93
Q

which opioid antagonist is more potent? naloxone or naltrexone?

A

naltrexone

used in treatment of alcohol addiction (mechanism unknown)

94
Q

plasma 1/2 life of naloxone?

A

1 hr in adults

95
Q

which drug is a competitive antagonist on all opioid receptors, has no tolerance effects, has a significant first pass effect, & is the drug of choice for reversing neonatal asphyxia from opioid use during labour?

A

naloxone

96
Q

latency to onset of naltrexone?

A

oral tablet = 15-30 min

97
Q

duration of action of naltrexone?

A

24-72 hours

98
Q

CIs to naloxone & naltrexone?

A
  • hypersensitivity
  • use cautiously w narcotic addiction, CV disease, lactating women, infants of opioid-addicted mothers
  • must not have taken any opiate for the last 7-10 days
  • may prevent action of opioid antidiarrheals, antitussives, and analgesics

Pharmacology (5 decks)

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