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PHAR255 > Pain 3 > Flashcards

Pain 3 Flashcards

1
Q

Differentiate opioids and opiates.

A

opioids: synthetic and semi-synthetic
-opiates
-oxycodone
-hydrocodone
-fentanyl
opiates: naturally derived from poppy seed
-opium
-codeine
-morphine
-heroin
all opiates are opioids but not vice versa

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2
Q

What are the main opioid receptor subtypes?

A

mu:
-analgesia, euphoria, physical dependence, respiratory depression, reduced GI motility (constipation), sedation
delta:
-analgesia, euphoria, physical dependence
kappa:
-analgesia, sedation, mood, does NOT contribute to physical dependence

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3
Q

What is the MOA of opioids?

A

bind to opioid receptors on the presynaptic primary afferent neuron to decrease Ca influx and decrease neurotransmitter release
-binding to opioid receptors in the CNS and PNS, suppressing neuronal firing from the presynaptic neuron and also inhibition of postsynaptic nerves in some areas, which alters transmission and perception of pain
-working in the brain and nerves to quiet and slow down pain signals, making it feel like there is less pain

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4
Q

What are the “big 5” of opioids?

A

morphine
codeine
hydromorphone
oxycodone
fentanyl

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5
Q

What are the indications for opioids?

A

symptomatic treatment of severe acute pain associated with surgery or medical conditions such as trauma, MI
symptomatic treatment of chronic and/or terminal cancer pain
management of dyspnea associated with respiratory secretions in patients chronic lung disease or terminal cancer
antitussive? (codeine)
opioid use disorder

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6
Q

What is the usual starting doses of opioids for use in acute pain?

A

codeine IR: 15-30mg q4h prn
morphine IR: 5-10mg q4h prn
hydromorphone IR: 1-2mg q4-6prn
tramadol IR: 50mg q4-6prn

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7
Q

What is the recommended dose and duration of opioids in acute pain?

A

lowest dose (should not exceed > 50 MEQ)
shortest duration

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8
Q

What are some basic considerations with opioid use in acute pain?

A

use with acetaminophen/NSAIDs
use with non-pharm strategies
lowest dose, shortest period
avoid driving & concurrent CNS depressants

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9
Q

What are the advantages of opioid use in chronic non-cancer pain?

A

potent analgesic effects
fast onset
relatively low risk of major organ toxicity

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10
Q

What are the disadvantages of opioid use in chronic non-cancer pain?

A

++ adverse effects
risk of diversion (community safety implications)
tolerance –> withdrawal mediated pain, escalating doses
long term evidence of benefit (>3mo) is lacking

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11
Q

What is the key takeaway from the SPACE trial?

A

opioids are not better for chronic back pain or knee OA

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12
Q

Differentiate between a strong and weak recommendation according to the Canadian Guidelines for Opioids for Chronic Non-Cancer Pain.

A

strong: all or almost all fully informed pts would choose the recommended course of action
weak: the majority of informed pts would choose the suggested course of action but an appreciable minority would not

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13
Q

What are the recommendations provided from the Canadian Guidelines for Opioids for Chronic Non-Cancer Pain?

A
  1. when considering therapy: optimize non-opioid pharm and non-pharm (strong)
  2. without current or past substance use disorder and without psychiatric disorders who have persistent pain despite optimized non-opioid pharm: add a trial of opioids rather than continued therapy (weak)
  3. with substance use disorder: we recommend against opioids (strong)
  4. with psychiatric disorder whose non-opioid therapy has been optimized: stabilize disorder before adding opioid (weak)
  5. history of substance use disorder whose non-opioid therapy has been optimized: continue non-opioid (weak)
    6 and 7. who are beginning long term opioid therapy: restrict prescribed dose to < 90 MEQ (strong), restrict starting dose to < 50 MEQ (weak)
  6. currently using opioid and have persistent problematic pain and/or problematic AEs: rotate opioids (weak)
  7. currently using > 90 MEQ/day: taper opioid to LED, potentially d/c (weak)
  8. experiencing serious challenge in taper: formal multidisciplinary program (strong)
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14
Q

What is the risk vs benefit of opioids in OA, chronic LBP, and neuropathic pain?

A

harms exceed the benefits

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15
Q

What are the formulations of opioids?

A

immediate release (IR)
sustained release (SR)
buccal/sublingual
suppository
transdermal
injection

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16
Q

What is the use of immediate release formulations of opioids?

A

used for acute pain, breakthrough pain, or when initiating someone on chronic therapy
duration: 4-6h
never fill SR for acute pain

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17
Q

What is the reference opioid?

A

morphine
-used for conversion factor calculations

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18
Q

How is morphine metabolized?

A

metabolized into two primary compounds (excreted in urine)
-morphine-6-glucuronide (active analgesic)
-morphine-3-glucuronide (not active as analgesic, CNS stim)

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19
Q

When do we need to be concerned about accumulation of morphines metabolites?

A

monitor closely or avoid if CrCl < 20-30ml/min
-accumulation of metabolites may lead to toxicity
-monitor for CNS toxicity, if occurs change to alt opioid
-if long-term opioid required, consider alt in pts with CKD

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20
Q

What is the potency of codeine?

A

much less potent than morphine
-MEQ=0.15

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21
Q

What is special about codeine?

A

it is a prodrug converted to morphine in body via CYP 2D6
-conversion required for analgesic effect

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22
Q

What is the significance of CYP 2D6 converting codeine to morphine?

A

~10% of population is deficient in CYP 2D6=no pain relief
ultra-rapid metabolizers=more AEs

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23
Q

What is a drug interaction of codeine?

A

agents that inhibit CYP 2D6
-less pain control

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24
Q

What is a caution of codeine?

A

breastfeeding
-rapid metabolizers –> morphine toxicity risk in infant

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25
Q

What are contraindications to codeine?

A

< 12 years old, < 18 years old post op tonsillectomy and/or adenoidectomy

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26
Q

What is codeine often found in combination with?

A

acetaminophen and caffeine

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27
Q

What is considered the antitussive dose of codeine?

A

> 15mg q4-6h

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28
Q

How potent is oxycodone?

A

1.5x more potent than morphine
-MEQ=1.5

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29
Q

How is oxycodone metabolized?

A

3A4 (major) and 2D6 (minor) to active metabolites
-increased AEs if ultra-rapid metabolizer

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30
Q

Differentiate OxyContin and OxyNeo.

A

OxyContin: d/c in 2012, route was easily altered
OxyNeo: bioequivalent to OxyContin, different formulation

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31
Q

How potent is hydromorphone?

A

5 times more potent than morphine
-MEQ: 5

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32
Q

Which opioid is a good option if the patient has renal impairment?

A

hydromorphone

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33
Q

What is the mechanism of action of tramadol?

A

dual mechanism of action:
-mu receptor agonist
-inhibits serotonin and norepinephrine reuptake

34
Q

What is tramadols affinity for the mu receptor?

A

~600 times less than morphine

35
Q

What is roughly the MEQ of tramadol?

A

MEQ: 0.1-0.2

36
Q

How is tramadol metabolized?

A

to a prodrug (O-desmethyl tramadol) via CYP 2D6

37
Q

What does tramadol increase the risk of?

A

seizures
serotonin syndrome
hypoglycemia
QT prolongation

38
Q

How potent is fentanyl?

A

much more potent than morphine (~100x)

39
Q

What do we mean when we say a fentanyl patch delivers 25mcg/hr which is equivalent to 100mg of oral morphine?

A

this is a daily equivalent
does NOT mean 100mg of morphine is released per hour
this conversion is safe when converting from opioid to fentanyl patch BUT conversion is aggressive when conversion from fentanyl patch to other opioid

40
Q

When is the fentanyl patch a good option for patients?

A

for those who cannot take oral medications & who are opioid tolerant

41
Q

What is the dosing schedule of the fentanyl patch?

A

q72hrs

42
Q

Is fentanyl metabolized to any active metabolites?

A

no known active metabolites
-option for patients with renal impairment

43
Q

What are situations where the fentanyl patch is less suitable?

A

diaphoresis
morbid obesity
ascites
cachexia

44
Q

What are counselling points regarding the fentanyl patch?

A

do not apply in front of children
remove old patch before applying new patch
apply to a clean, dry, non-hairy skin area on the chest, back, flank, or upper arm
if required, clip hair as close as possible to the skin (do not shave)
avoid sensitive areas or areas of excessive movement
do not use external source of heat on top of the area while patch is on
when placing on skin, hold firmly x 30s
-if it falls off, discard and use a new one on different site
remove patch after 3 days
new patch should be applied to a different place on the skin
when disposing, fold in half and place in container for pharmacy to dispose

45
Q

Which fentanyl patch should be used for dosing titrations/tapers?

A

12mcg/hr patch

46
Q

Which type of fentanyl patch can be cut if needed?

A

matrix membrane patch
-not officially recommended, inaccurate dosing
-monograph says it should not be cut

47
Q

What is the MOA of methadone?

A

potent mu opioid receptor agonist and an NMDA receptor antagonist
-NMDA mechanism plays a role in prevention of opioid tolerance, potentiation of analgesic effects, & neuropathic pain treatment

48
Q

What is the half-life of methadone for pain?

A

long and variable: ~10-60h (24-190h for some)
-potential for accumulation and overdose
-do not increase dose more frequently than q3-5d

49
Q

What is the duration of analgesia from methadone?

A

6-12 hours
-usually dosed q8h for pain, differs from OD dosing for opioid use disorder

50
Q

When should methadone use be cautioned?

A

severe hepatic failure
hepatitis
concurrent antiretroviral use

51
Q

Is methadone viable in renal impairment?

A

yes
-inactive metabolites are excreted in urine and feces

52
Q

What are risks with methadone?

A

QTC prolongation
-initiating prescribers should generally obtain an ECG at baseline
-certain risk factors require an additional ECG
serotonin syndrome when combined with serotonergic drugs

53
Q

What is the maximum recommended starting dose of methadone?

A

30mg/day

54
Q

Describe methadone in the context of opioid use disorder.

A

slow onset: progression of respiratory depression is insidious
24h t1/2: serum lvls will increase with each dose until steady state is achieved
-increased risk of overdose and death
-should not increase dose more frequently than q5d
physiological dependence–>physical and psychological withdrawal symptoms if d/c abruptly

55
Q

What are the receptor interactions of buprenorphine?

A

mu-partial agonist, delta & kappa antagonist
-analgesia, decreased opioid-induced hyperalgesia & tolerance
-better safety profile
-may cause less anxiety & depression
high affinity, slow dissociation, long t1/2
-more consistent serum concentrations, can alleviate end-of-dose withdrawal
-flexibility in dosing schedules

56
Q

How is buprenorphine metabolized?

A

CYP 3A4 substrate (major)
-safe in decreased renal function
-relatively safe with hepatic dysfunction

57
Q

What are the contraindications to opioids?

A

allergy
co-administration of a drug capable of inducing drug-drug interaction
active diversion of controlled substances

58
Q

Differentiate between a pseudoallergy and a true opioid allergy.

A

pseudoallergy
-common
-flushing, itching, hives, sweating, hypotension
-result of histamine release
-options: nonopioid analgesic, lower dose, alternate opioid, add H1 or H2 blocker
true opioid allergy
-rare
-severe hypotension, breathing/swallowing difficulties, swollen lips/face/aiways
-options: change to nonopioid or opioid from different class

59
Q

What are the general adverse effects of opioids?

A

sedation
respiratory depression
constipation
nausea
miosis (pinpoint pupils)
itching/rash (pseudoallergy)

60
Q

Which side effects do patients not develop tolerance to from opioids?

A

patients will develop tolerance to all adverse effects of opioids except constipation and miosis

61
Q

What is the risk with tolerance to respiratory depression from opioids?

A

tolerance to respiratory depression can be lost quickly within 1-2 days of no opioids –> high risk for overdose if return to previous dose

62
Q

Describe tolerance to sedation from opioids.

A

begins after 3-4 days
may take up to 10 days
highly variable, may never resolve

63
Q

What are the long term adverse effects of opioids?

A

can occur as short as weeks:
-hypogonadism
-sleep apnea
-opioid induced hyperalgesia
-opioid tolerance
-opioid dependence, opioid use disorder
-risk of opioid toxicity

64
Q

What are the serious drug interactions of opioids?

A

CNS depressants
MAOIs
drugs that prolong QT
serotonin syndrome with serotonergic drugs
carbamazepine + tramadol = seizure risk
gabapentin and pregabalin

65
Q

Describe hypogonadism due to opioids.

A

opioids influence the HPA axis and the HPG axis
-morphine has been reported to cause a strong, progressive decline in plasma cortisol level
-opioids interfere with modulation of hormonal release including: increase in prolactin, decrease in LH, FSH, test/est
-testosterone depletion has been demonstrated in people with opioid use disorder and in pts receiving methadone maintenance therapy

66
Q

What can the collective effects of hormonal changes from opioids lead to?

A

decreased libido and drive
aggression
amenorrhea or irregular menses
galactorrhea

67
Q

Describe sleep apnea due to opioids.

A

patients on long-term SR opioids show a distinctive pattern of sleep-disordered breathing call central sleep apnea that is different from disturbances observed in OSA
the oxygen desaturation is more severe and respiratory disturbances are long during NREM sleep
opioids may complicate underlying sleep apnea and make CPAP less effective

68
Q

Describe opioid tolerance.

A

may have reduced effect over time
withdrawal-mediated pain is becoming increasingly understood
-mechanism still unclear
may result in end-of-dosing interval increase in pain
-beyond underlying pain severity

69
Q

Describe opioid-induced hyperalgesia.

A

increased sensitivity to pain
even after one month of opioid therapy in pts with chronic pain
appears to be more likely with higher doses of opioids for longer periods of time
mechanism unclear but speculated to be related to NMDA receptor sensitization, increased glutamate release, and immune cell changes

70
Q

How do we manage opioid-induced hyperalgesia?

A

consider dose reduction (taper), opioid rotation (account for cross-tolerance), rotation to buprenorphine or methadone

71
Q

What might the risk of iatrogenic opioid use disorder be associated with?

A

history of substance use disorder
taking opioids for > 90 days
taking higher doses ( > 120 MED)

72
Q

According to POMI and COMM, what are positive screens for opioid use disorder?

A

POMI: score > 2
COMM: score > 9

73
Q

What are the signs and symptoms of opioid overdose?

A

difficulty walking, talking, staying awake
blue lips or nails
very small pupils
cold and clammy skin
dizziness and confusion
extreme drowsiness
choking, gurgling, or snoring sounds
slow, weak or no breathing
inability to wake up, even when shaken or shouted at

74
Q

What is a proper response to opioid overdose?

A

call 911
give naloxone
an overdose is always an emergency

75
Q

How does naloxone work?

A

binds the same sites as opioids in the brain
-displaces opioid
-antagonist at receptor
restores breathing within 2-5min when it has been dangerously slowed or stopped due to opioid use

76
Q

True or false: IM naloxone can be given through clothing into the muscle of the upper arm or upper leg

A

true

77
Q

What can occur with naloxone in someone with opioid dependence?

A

can cause opioid withdrawal
-benefit > risk

78
Q

How long do the effects of naloxone last?

A

30-90min, so overdose may return
-especially if taking a long acting opioid

79
Q

Why is opioid use challenging with acute on chronic pain?

A

challenging due to opioid tolerance & potential hyperalgesia

80
Q

What is the management of acute on chronic pain in people using opioids?

A

educate patient
-pain relief aimed at acute pain
maintain analgesia for underlying pain condition
may use short acting opioids for new ACUTE pain
use adjuvant analgesics (acet, NSAIDs, ketamine, gabapentin)
return to prior analgesic dose when acute pain resolved

PHAR255 (24 decks)

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