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Neurology > Opiod Cases > Flashcards

Opiod Cases Flashcards

1
Q

Types of pain management and their sites of action

A

1) NSAIDs
- work on the periphery and spinal level
- better for fissure injuries rather than nerve injuries and neuro pain

2) COX-2 inhbitors
- same as 1

3) opioids
- work on the superaspinal and spinal level
- better for nerve injuries and CNS pain

4) anticonvulsants and tricyclic antidepressants
- same as 3

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2
Q

How do opioids work?

A

Reduce transmission of the pain in the spinal cord to the brainstem and lowers perception of pain in cortex

They raise the threshold of pain and inhibit signals

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3
Q

U-opioid receptors (MOR)

A

Can work to increase K+ conductance, decreases ca 2+ activity or decrease activity of cAMP/PKA

All of these suppress depolarization of pain nerves

Also has the following effects

  • inhibits respiration (bradycardia)
  • slows GI trains
  • modulates hormone and neurotransmitter release
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4
Q

D-opioid receptors (DOR)

A

Can work to increase K+ conductance, decreases ca 2+ activity or decrease activity of cAMP/PKA

All of these suppress depolarization of pain nerves

Also have the following effects:
-modulate hormone and neurotransmitter release

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5
Q

K-opioid receptor (KOR)

A

Works to decrease calcium channel activity or decreases generation of cAMP and PKA

All of these suppress depolarization for nerves of pain.

Also has the following effects:

  • psychotomimetic effects
  • slows GI transit
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6
Q

Mechanisms of action of u-opioid receptor agonists at the spinal cord levels

A

Activation of MORs on presynaptic fibers results in dampened great the glutamate signals

Reduces glutamate and substance P releases which lowers pain signaling

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7
Q

Mechanisms of action of u-opioid receptor agonists at the brainstem levels

A

Induces supraspinal analgesia by hyperactivity of inhibitory descending fibers

Causes inhibition of excitatory neurons

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8
Q

Mechanisms of action of u-opioid receptor agonists at the thalamus levels

A

Induces agonism of u-opioid receptors in thalamus which causes reduced glutamate release in the cortex

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9
Q

What parts of the telencephalon and diencephalon do opioids work on

A

Thalamus

Cerebral cortex

Amygdala

Hippocampus

overall reduces emotional reactivity and perceptions to pain

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10
Q

What natural produced pain tolerance peptides are produced by the body

A

Enkephalins

Endorphins

Dynorphins

  • these are produced by pre-propeptides*
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11
Q

What are the affinities for the natural pain tolerance peptides for each opioid receptor?

A

MOR = endorphins > enkephalins > dynorphins

DOR = enkephalins > endorphins = dynorphins

KOR = dynorphins&raquo_space; endorphins = enkephalins

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12
Q

What is the main derivative/ prototype of exogenous opioids?

A

Morphine

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13
Q

Why are MOIs (monoamine oxidase Inhibtors) contraindicated as a coconmittal use with opioids?

A

Causes hyperpyrexic comas and/or HTN as a result

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14
Q

What the metabolism of most opioids?

A

Glucuronidation in the liver followed by renal excretion

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15
Q

What opioids are activated by CYPs?

A

Codeine

Oxycodone

Hydrocodone

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16
Q

What are the general contraindications for opioids

A

Concomitant use of agonists with partial agonists
- causes diminished effects and can both induce withdrawal or increase ADRs

Patients with head trauma
- increases intracranial pressure to dangerous levels

Pregnant patients
- baby becomes dependent on the drug

Impaired pulmonary/hepatic/renal functions
- causes respiratory distress and possible OD respectively

Patients with endocrine diseases
- causes increased apparent doses and possible overdoses

17
Q

Stage 1 of opioid withdrawal

A

Lasts up to 8 hrs

Includes

  • anxiety
  • drug cravings
18
Q

Stage 2 of opioid withdrawal

A

Lasts up to 8-24 hrs

Includes:

  • anxiety
  • insomnia
  • GI distress
  • rinhorrhea
  • mydriasis
  • diaphoresis
19
Q

Stage 3 of opioid withdrawal

A

Lasts up to 3 days

Includes

  • tachycardia
  • nausea/vomiting
  • HTN
  • diarrhea
  • fever
  • chills
  • tremors
  • seizures
  • muscle cramps
20
Q

Buprenorphine

A

Partial agonist of MOR

Partial antagonist of KOR

used for mild-moderate pain only
only partial agonist

Can precipitate withdrawal symptoms and is useful in concomitant useage with naloxone for detox

21
Q

Methadone

A

Synthetic opioid which blocks NMDA receptors and monoamine reuptake transports

Used for detoxification to limit withdrawal symptom magnitude

22
Q

Morphine

hydromorphone, oxycodone, hydrocodone

A

Potent agonist of MOR

Distributes well within the BBB

useful adjunct in pulmonary edema and general anesthesia

23
Q

Fentanyl

A

80-100 times stronger than morphine but works the same way (agonist of MOR)
- very easy to OD

Administered orally

Metabolized by CYP3A4

very high risk of respiratory distress and CNS depression if overdosing

24
Q

Codeine

A

Common antitussive agent that is often do formulated with NSAIDs

Mild MOR agonist, mainly used for antitussive effects

is metabolized by the CYP2D6 enzymes to become morphine (since it is a prodrug of morphine)

Morphine/codeine is eliminated via hepatic glucuronidation and renal excretion

25
Q

Codeine effects w/ poor CYP2D6 and hyperactive CYP2D6 metabolizes

A

Poor = no analgesic effect
- not converted into morphine

Hyperactive = increased apparent dose of morphine

26
Q

What other opioid pro drugs are common?

A

Oxycodone -> oxymorphone
- more potent morphine

Hydrocodone -> hydromorphone
- more potent morphine

Heroin -> morphine + 6-monoacetylmorphine
- very potent metabolite

27
Q

What are the 2 metabolites from morphine metabolism?

A

M6G
- produces analgesic effect in accumulation

M3G
- produces seizures in accumulation

both are renally excreted, so must be careful with patients who have renal dysfunctions

28
Q

Meperidine

A

A potent MOR agonist W/ rapid onset

CONTRAINDICATED in extended use overall, renally impaired patients and patients with tachycardia

  • not a 1st line agent either
  • leads to seizures and arrhythmias
29
Q

How does loperamide work for diarrhea (it’s intended use)

A

Activation of MOR receptors on excitatory neurons and secretomotor neurons
- causes constipation and decreased secretions

30
Q

What is the difference between methylnaltrexone and naltrexone

A

Methylnaltrexone’s methyl group makes it not able to cross the BBB
- only acts on the periphery

Both are MOR/DOR/KOR antagonists

Neurology (65 decks)

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