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*Pharm > Opioids > Flashcards

Opioids Flashcards

1
Q

What do we use opioids for in anesthesia?

A
  1. dec SNS response to noxious stimuli
  2. adjunct w/ inhalational gas to dec anesthetic dose
  3. sole (fent/sufent/morph - cardiac anesthesia/critically ill)
  4. peri-op/post-op pain
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2
Q

Where do opioids work?

A

supraspinal - modulate pain in brain
spinal - direct pain modulation in dorsal horn
peripheral - peripheral terminals of nociceptive neurons

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3
Q

describe brain pain modulation

A

descending inhibitory pathway
periaqueductal gray, amygdala, crpus striatum, hypothal send projections to raphe magnus who send projections down SC to interneurons in substantia gelatinosa

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4
Q

What is TRYPV1

A

nociceptive receptor for thermal/chemical stimulus

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5
Q

Describe how TRYPV1 works

A
  • stimulus binds to TRYP1 receptor, influx of Na+/Ca+ cause depolarization and release of bradykinin, PGs, etc
  • bradykinin and PGs (inc Na+ influx) inc sensitivity to stimuli
  • w/ opioids they bind to mu receptor and inc K+ eflux = hyperpolarization = dec stimulus
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6
Q

What makes opioids unique from other analgesics?

A
  • they have no ceiling effect, no max dose, s/e limit
  • can develop tolerance
  • cross-tolerance
  • analgesia w/o loss of touch, proprioception, consciounsness
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7
Q

What are the naturally occurring opioids?

A

-morphine and codeine

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8
Q

What are the semisynthetic opioids?

A

-heorin and dihydromorphone

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9
Q

describe agonist, partial agonist, mixed agonist/antagonist, antagonist

A
  • agonist - mimics
  • partial agonist - no matter how much you give will only give partial response
  • mixed - i.e. agonist at kappa receptor and antagonist at mu receptor
  • antagonist - inhibits
  • pt already on partial agonist and you give full agonist then full may not be as effective bc of competition
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10
Q

mechanism of action: opioids

A

pre-synaptic - inhibit excitatory NT release (ach, DOPA, NE, sub P)
post-synaptic - inc K+ conductance (hyperpolarize), inactivate Ca+ channel (dec NT release), PLC cascade, inhibit adenyle and dec cAMP

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11
Q

What type of receptors are opioids?

A

GPCR

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12
Q

Describe Mu opioid receptors:

Mu

A

Mu1 - spinal/supra/periph

  • works w/ all endo/exo opioids agonist
  • causes euphoria, bradycardia (good for cardiac cases to dec myo O2 consumption and balance supply and demand), miosis, urinary retention, hypothermia

Mu2 - spinal (some supra)

  • works w/ all endo/exo agonists
  • hypoventilation, physical dependence, constipation
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13
Q

Describe Kappa/Delta receptors

A

Kappa - spinal/supra/periph

  • works with Dynorphins (endogenous)
  • opioid agonist-antagonist work at kappa receptor
  • dysphoria, sedation, miosis, diuresis

Delta - spinal/supra/periph

  • enkaphalins (endogenous)
  • hypoventilation, constipation, urinary retention
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14
Q

2 reasons why people have variable responses to opioids

A
  1. genetic mutation (SNP) on mu receptor affecting opioid agonist binding and pain response
  2. CP450 system mutation that alters metabolism of:
    [C.H.O.M.] CODEINE, HYDROCODONE, OXYCODONE, METHADONE = unpredictable PK’s
    FENTANYL is least likely to be affect = predictable
    **rate of metabolism may affect s/e - fast metabolizers have inc postop n/v
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15
Q

What are perioperative CV effects of opioids?

A
  • minimal but inc if combined w/ other anesthetics
  • dose-dependent BRADYCARDIA; opioids cause vagal stimulation that promotes SA/AV node depression
  • VASODILATION (dec SVR) d/t impaired SNS response/tone causing dec CO/BP w/ venous pooling (orthostatic hypotension); inc w/ hypovolemia (=NPO pts)
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16
Q

What is unique about morphine and meperidine (demerol) w/ CV effects?

A
  • both cause dose dependent and infusion dependent histamine release (itching)
  • histamine causes bronchospasm and (vasodilation) dec SVR/BP
  • *do not use w/ asthmatics

-meperidine - causes TACHYCARDIA w/ direct myocardial depression (diff than all)

17
Q

What are perioperative CNS effects of opioids?

A
  • analgesia, euphoria, drowsiness, miosis, nausea (d/t chemoreceptor trigger zone)
  • NO amnesic effect
  • can dec ICP/CBF if hypoventilation avoided
  • i.e. pt. w/ head bleed or tumor given opioid begins to hypoventilates = inc co2, might push them over the edge. If you give an opioid with pts. with icp issue, make sure they don’t develop decrease respiration
18
Q

What are perioperative Renal/GI/Liver effects of opioids?

A
  • urgency with retention
  • dec catecholamine and cortisol (dec stress respone = good)
  • sphincter of Oddi spasm and GB contraction (can mimic angina)
  • constipation d/t GI sm muscle spasm/dec motility
  • n/v d/t dec gastric emptying, chemoreceptor trigger zone (4th ventricle)
19
Q

Pruritis and opioids

A
  • unknown cause
  • probable d/t histamine release
  • “fentanyl nose itch”
20
Q

What are perioperative skeletal muscle effects of opioids?

A
  • wooden chest syndrome = muscle rigidity chest/abd/jaw/extremities
  • common w/ large/rapid doses of F.S.H. = fent/sufent/hydro
  • difficult ventilation > need intubation
  • high a/w pressure from inc intrathoracic pressure = dec venous return
21
Q

What are perioperative ventilatory effects of opioids?

A
  • dose dependent resp depression (#1 cause of death)
  • small dose = inc TV, dec RR = dec MV
  • large dose = dec TV, dec RR
  • dec chest complaince
  • pharyngeal/laryngeal constriction
  • cough suppression
  • dec response to hypercarbia and hypoxia
  • bronchospasm from morphine/meperedine histamine release
22
Q

What happens to the ventilatory response curve to morphine??

A

its reduced and shifted to the right (#1 cause of death)

23
Q

Morphine

A
  • severe acute pain
  • PO used mainly for chronic/cancer pain
  • large first pass effect; converted to active metabolite (same effect as morphine)
  • e 1/2 life = 3-4 hours
24
Q

Codeine

A
  • e1/2t = 3 hrs
  • combo with APA, guaifenesin, promethazine
  • is a PRODRUG; 10% is metabolized to its active form (MORPHINE), rest is inactive metabolite
  • lack of 2D6 = no analgeis ceffect (caucasians/asians)
  • antitussive effect thruout conversion (better for cough than pain)
25
Q

Hydrocodone

A
  • chronic pain
  • always w/ APAP, ASA, ibu, antihistamine
  • antitussive/analgesic
  • high abuse potential
26
Q

Oxycodone

A
  • mod to sev pain, chronic, post-op pain
  • combo with APAP (percocet) or ASA (percodan)
  • oxycontin = ERelease
  • no active mtabolites, safer w/ renal patients
  • high abuse potential
27
Q

Methadone

A
  • PO/IV/SQ
  • synthetic
  • long 1/2l and unpredictable(8-100 hours!!!)
  • treats opioid addiction daily
  • no active metabolites, safer w/ renale pts
  • used for chronic pain syndrome i.e. neuropathic pain - dose BID or TID
  • risk for resp depression d/t long 1/2l
28
Q

When does opiod tolerance tend to occur?

A

-chronic use after 2-3 weels

29
Q

What does pt notice w/ opioid tolerance?

A
  • red adv effects (including resp/CNS depression)
  • shorter DOA
  • dec effectiveness
30
Q

What is cross-tolerance?
How do you switch opioids w/ CT?
What about s/e w/ CT?

A
  • cross tolerance is when pt is tolerant to another opioid agonist; can occur w/ all full agonists but is not complete
  • when switching to other opioid start w/ HALF or lower dose
  • can try switching opioid-tolerant patients to methadone
  • tolerance to constipation does not occur - Rx laxative w/ or w/o SS
31
Q

What happens when someone who is physically dependent on opioids suddenly stops taking them?

A
  • causes abstinence symptoms to occur

- MUST TAPER

32
Q

Difference b/n tolerance and dependence and addiction

A

tolerance - body becomes tolerant to effects of drug
dependence - body physiologically dependent on drug and abrupt d/c can cause physiologic issues
addiction - PSYCHOLOGICAL dependence and social factors (requiring higher doses = tolerance not addiction)

33
Q

When does dependence tend to develop?

A

several weeks after chronic trx

34
Q

What do neuraxial analgesia target?

A

mu receptors in substantia gelatinosa AND into vasculature for systemic effect

35
Q

Where can opioids go w/in epidural space vs spinal?

A
  • epidural space can have uptake in fat, systemic absorption or diffusion into CSF
  • spinal is directly into CSF (spinal) w/ diffusion into vasculature
36
Q

Difference in rate of uptake between highly lipid soluble vs. less lipid soluble

A
  • high lipid soluble (i.e. FENTANYL) is limited in flowing cephalad by fast absorption into spinal cord
  • systemic effects develop faster d/t faster diffusion
    (i. e. resp depression can occur w/in 1 hour )
  • less soluble (i.e. MORPHINE) remains in CSF for transfer to cephalic location
  • systemic effects develop slower d/t slower diffusion (i.e. slow to reach brain where it causes resp depression w/in 12-24 hrs)

-Same things w/ epidurals - but will be slower cause it needs to travel to the veins

37
Q

What is dose of epidural compared to spinal?

A

epi is 5-10x higher thans pinal (epi has lot of fat and does not go into CSF)

*Pharm (6 decks)

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