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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
which opioid is an antagonist? | affinity for binding but no efficacy; blocks action of endogenous & exogenous ligands
naloxone, naltrexone
26
absorption of opioid drugs
- well absorbed via GIT ; often given parenterally | - IM injections no longer recommended
27
``` time (latency) to onset: oral intranasal IV pulmonary-inhalation ```
oral: 15-30 mins intranasal: 2-3 minutes IV: 15-30 seconds pulmonary-inhalation: 6-12 seconds
28
which 2 opioids have active metabolites after phase I detox?
morphine | codeine
29
opioid elimination primarily via?
kidney
30
CIs for opioid use?
``` increased intracranial pressure decreased ventilation (COPD, cor pulmonale, emphysema, asthma) hx opiate addiction/allergy ```
31
precautions in dosing opioids needed in these 5 cases
``` elderly debilitated under 18 yrs of age renal/hepatic disease opioid naive (not been taking opioids regularly) ```
32
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)
LIMBIC (emotional)
33
what kind of pain are opioids most effective in relieving?
dull, diffuse, continuous pain
34
Opiates suppress the "_____ center" which is also located in the brainstem, the medulla. esp. which drug?
cough center esp. codeine
35
how do opioids cause constipation?
- delays gastric emptying - causes spasmodic increases in intestinal smooth muscle tone - reduces intestinal secretions - increases anal sphincter tone
36
most serious side effect of opioids?
respiratory depression | principal cause of death
37
9 adverse effects of opioids?
``` respiratory depression constipation nausea endocrine effects miosis (papillary constriction) euphoria itchiness (increased histamine release) tolerance physical dependence ```
38
what are adverse effects on endocrine system?
``` inhibits GRH (lowers LH, T) inhibits release of antidiuretic hormone ```
39
tolerance develops to which side effects of opioids?
respiratory effects analgesic effects euphoric effects sedative effects no tolerance to miosis /constipation effects
40
2 drug interactions and 1 CI?
sedative hypnotics - increased CNS depression (esp. resp) TriCyclicAntidepressants & antipsychotic drugs - increase sedation CI: MAOI - high incidence of hyperpyrexic coma
41
morphine has high binding affinity for which receptors and less affinity for which 1 receptor?
high - mu and delta | weak - kappa
42
how is morphine administered?
subcutaneous intravenous epidural injections orally in solution (far less potent)
43
which is faster acting? morphine or codeine?
codeine
44
which is faster acting? morphine or heroin?
heroin
45
latency to onset of morphine?
15-60 mins
46
duration of action of morphine?
3-6 hours
47
why does oral dosing of morphine have poor availability?
first-pass metabolism
48
how much morphine is protein-bound in blood?
30%
49
major pathway for metabolism of morphine (excretion)
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
which morphine metabolite is responsible for interactions with opioid receptors?
morphine-6-glucoronide
51
latency to onset of hydromorphone?
15-30 mins
52
duration of action of hydromorphone?
3-4 hours
53
peak effect of hydromorphone felt after how long?
30-60 mins
54
hydromorphone is how many times more potent of an analgesic than morphine?
7-10 times
55
fentanyl routes of administration?
oral transdermal possibly IV
56
latency to onset of fentanyl?
7-15 mins oral | 12-17 hours transdermal
57
duration of action of fentanyl?
1-2 hours oral | 72 hours transdermal
58
what percentage of fentanyl is protein-bound?
80-85%
59
how much of fentanyl is metabolized in liver to inactive metabolites?
90%
60
fentanyl is how many times more potent of an analgesic than morphine?
80 times! | 100 micrograms of fentanyl approximately equivalent to 10 mg of morphine
61
fentanyl is how many times more potent of an analgesic than hydromorphone?
10 times
62
fentanyl has high efficacy for which receptors?
mu 1 receptors
63
which opiate is the most effective analgesic?
fentanyl
64
codeine is x/6 as strong as morphine x=?
1/6 as strong
65
explain codeine metabolism
converted to morphine by 2D6 --> renal elimination | converted to codeine-6-glucoronide 3A4 --> renal elimination
66
what is the more common name of diacetylmorphine?
heroin
67
metabolism of heroin
heroin (diacetylmorphine) --> 6-monoacetylmorphine --> morphine --> morphine-3-glucoronide or morphine-6-glucoronide
68
heroin binds most strongly to which receptor?
mu receptor
69
Heroin produces_________ effects similar to morphine, however, it is thought that these effects are greater and more addicting because of its _____________.
euphoric effects extremely rapid effect.
70
why is heroin so fast-acting?
it is extremely lipid-soluble because of its acetyl groups and therefore it immediately crosses the blood brain barrier
71
physiologically, how is a dependence on heroin created?
causes body to produce far less endorphins (natural opioid peptides)
72
withdrawal symptoms of heroin
``` 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
what is cross-tolerance & give an example
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
why administer methadone in heroin withdrawal?
methadone maintenance programs allow heroin users the opportunity to maintain a certain level of functioning without the withdrawal reactions
75
withdrawal reactions are usually the __________ of the physiological effects produced by the drug
opposite
76
examples of opioid withdrawal reaction?
``` pain & irritability hyperventilation dysphoria & depression restlessness & insomnia hostility increased blood pressure diarrhea pupillary dilation spontaneous ejaculation chilliness & "goose flesh" ```
77
list 3 synthetic opioids
hydrocodone (vicodin) meperidine (demerol) methadone
78
which opioid analgesic is 10,000 times more potent than morphine and is used as a tranquilizer for large animals?
carfentanil
79
vicodin is a solution of which 2 meds?
acetaminophen + hydrocodone
80
place these in order of weakest to strongest: vicodin morphine codeine
codeine --> vicodin --> morphine
81
what is a common side effect of demerol?
severe nausea and vomiting
82
why has demerol fallen out of favour in recent years?
it has a neurotoxic metabolite
83
percentage-wise, how much of an analgesic effect does demerol have as compared to morphine?
10%
84
compare demerol (meperidine) to morphine
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
is methadone addictive?
synthesized to not have euphoric properties and mild withdrawal effects is still addictive.
86
compare methadone, codeine & morphine half lives
methadone: 24-48 hours morphine: 2-4 hours codeine: 2-4 hours
87
methadone is an analog of which compound?
codeine
88
CIs for narcotic analgesics?
- 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
use narcotic analgesics cautiously with whom?
- 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
list 2 opioid antagonists
naloxone | naltrexone
91
list 3 effects of opioid antagonists
- 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
what are opioid antagonists used to treat?
opioid overdose
93
which opioid antagonist is more potent? naloxone or naltrexone?
naltrexone | used in treatment of alcohol addiction (mechanism unknown)
94
plasma 1/2 life of naloxone?
1 hr in adults
95
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?
naloxone
96
latency to onset of naltrexone?
oral tablet = 15-30 min
97
duration of action of naltrexone?
24-72 hours
98
CIs to naloxone & naltrexone?
- 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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