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Anesthesia > Opioids > Flashcards

Opioids Flashcards

1
Q

What are the naturally occurring opioids?

A

Morphine

Codiene

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2
Q

What are the opioid receptors?

A

Mu
Kappa
Delta

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3
Q

What are the endogenous opioids?

A

encephalin
endorphin - mu
dynorphin - Kappa

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4
Q

Mu-1 receptor responsible for what effects?

A

Analgesia

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5
Q

Mu-2 receptor is responsible for what effects?

A

hypoventilation
bradycardia
physical dependence

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6
Q

Kappa receptor is responsible for what effects?

A

dysphoria
diuresis (- reg of ADH)
may antagonize some of the effects at the Mu receptor
Natural ligand is dynorphin

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7
Q

What function does delta receptors have?

A

modulate mu receptor activity

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8
Q

Describe the intracellular action of opioid receptor activation

A

coupled to G proteins

  1. reduction of intracellular cAMP and inhibition of voltage-gated calcium channels = decreases intracellular calcium
  2. activates K+ (inward rectifier)
  3. Activates MAPK

net result is decreased neuronal transmission

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9
Q

How does lipid solubility affect onset of opioids?

A

Higher lipid solubility = faster onset (fentanyl)

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10
Q

Which two opioids may require decreased dosing in renal failure due to active metabolites?

A

Meperidine –> normeperidine –> SEIZURES in patients with renal failure

Morphine –> morphine-6-glucuronide, which may accumulate in neonates and those with renal failure –> Resp depression

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11
Q

What aspect of the molecular structure of remifentanil influences its primary mode of metabolism?

A

Ester linkage –> rapidly metabolized by plasma and red blood cell esterases (NOT affected by atypical or pseudocholinesterase deficiency)

= shortest acting of all opioids

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12
Q

How does the lipid solubility of an opioid effect is time to onset and duration when administered in the epidural space?

A

Epidural - requires diffusion across dura, requires 5-10x dose vs. intrathecal

Lipid soluble drugs like fentanyl - more rapid absorption and shorter duration of action

More water-soluble drugs like morphine = longer onset and duration of action

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13
Q

What are the effects of opioids on circulation and how does meperidine differ from most opioids?

A

bradycardia from stimulation of the central vagal nucleus

morphine–> histamine from mast cells –> peripheral vasodilation and hypotension

hypovolemic patients - orthostatic hypotension d/t impairment of the compensatory sympathetic nervous system

Meperidine, in contrast to other opioids –> tachycardia, may be related to its structural similarity to atropine and mydriasis

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14
Q

What are the effects of opioids on the GI tract?

A

reduce biliary, pancreatic, and intestinal secretions
increase resting tone in intestines –> increase in nonpropulsive contractions (bowel spasm)

net effect = slow passage of intestinal contents, increase their viscosity, and induce constipation

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15
Q

What are the effects of opioids on the eyes?

A

pupillary constriction (miosis)

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16
Q

What are the effects of opioids on the MSK system?

A

Skeletal muscle rigidity can occur after a rapid intravenous bolus - usually fentanyl

Vocal cord closure

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17
Q

What is opioid tolerance?

A

a reduction in opioid effect over time (2-3weeks)

or an increase in dose over time for the same desired effect

18
Q

Define opioid dependence

A

development of a withdrawal syndrome (agitation, diarrhea, and hyperalgesia) with abrupt cessation and/or administration of an antagonist (e.g. naloxone).

Ave. 25 days

19
Q

Define opioid addiction

A

drug-seeking behavior motivated by strong efforts to acquire the drug for non-therapeutic self-administration

Behaviors:

  • continued use despite harm
  • compulsive use
  • craving
  • selling, forgery, stealing
20
Q

What is hyperalgesia and how does it relate to tolerance?

A

an increase in the magnitude of pain experienced from any given painful stimulus - can occur after stopping an opioid (REMI)

This is a variant of tolerance

21
Q

How can one reduce the incidence of hyperalgesia?

A

use NMDA-agonists such as ketamine
methadone (also a u-opioid agonist)
COX-2 inhibitors.

22
Q

How is Naloxone administered for opioid overdose?

A

0.4-2mg every 2-3 minutes as needed

23
Q

What is unique about methylnaltrexone?

A

opioid agonist-antagonist that does not cross the BBB

used to tx constipation for those on chronic narcotics

24
Q

What are the effects of opioids on respiration?

A

Depression

  • alter vent response to CO2 in medulla
  • Low threshold where patient becomes apneic (40mmHg)
25
Q

What are the effects of opioids on urinary system?

A

Urinary retention

  • > males
  • > intrathecal or epidural
  • inc sphincter tone, dec bladder tone
26
Q

What are the effects of opioids on testosterone and cortisol?

A

Decreases

27
Q

What drug is a pro-drug metabolized to morphine?

A

Codeine

10% of population has low CYP2D6 = not metabolized = no effect

28
Q

What receptors does Meperidine act and its main use?

A

Post-op shivering (a-2 agonist)

Serotonin re-uptake inhibitor

29
Q

Where is can large stores of inactive fentanyl develop?

A

Lungs

30
Q

What form of fentanyl has no 1st pass effect and higher [peak]?

A

Oral transmucosal fentanyl citrate

31
Q

How is alfentanil metabolized?

A

CYP3A4 - significant variability b/w people

32
Q

What is the most potent opioid?

A

Sufentanil = 1000x stronger than morphine

Some post-op analgesia (longer context sensitive half-time vs. Remi)

33
Q

At what receptors does methadone act?

A
  • L-isomer = opioid agonist
  • D-isomer = NMDA antagonist
  • Serotonin & NE reuptake inhibitor
34
Q

What is the half-life of methadone?

A

About 35 hours!

35
Q

How does alfentanil compare to fentanyl in terms of potency, onset and duration?

A

1/5-1/10 as potent

More rapid onset (1.5min)

Shorter duration

36
Q

Which opioid has anticholinergic properties?

A

Meperidine - atropine-like structure

37
Q

What opioids are contraindicated with MAOIs (selegiline)?

A

Meperidine, methadone and tramadol —> serotonin syndrome

38
Q

Best method for post-op pain control in patient on Naltrexone?

A

Stop 24 hours b4 surgery (its duration of action)

39
Q

What signs and symptoms do NOT develop tolerance with opioid use?

A

Miosis and constipation always will occur

40
Q

What is the mechanism of action of Tapentadol (Nucynta)

A

NE-reuptake inhibitor
Mu agonist

Do not use w/ MAOIs, SSRIs

Anesthesia (25 decks)

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