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CA1 > Narcotics > Flashcards

Narcotics Flashcards

1
Q

How is analgesic different from anesthetics

A

Analgesics - relief from pain
Anesthetics - eliminates all sensation including pain

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2
Q

What determines choice of analgesia

A

Type of pain eg neuropathic pain responds better to TCAs/AEDs, migraine responds better to triptans and NSAIDs
Severity of pain
Response to other analgesics

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3
Q

What are the endogenous opioid receptors

A

Mu, kappa, delta

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4
Q

What are endogenous opioid peptides

A

endorphin, enkephalins, dysnorphins

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5
Q

Types of opioid analgesics

A

Full agonist, partial agonist and antagonists

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6
Q

Central and peripheral location of receptors do what?

A

Modulates pain
Inhibit respiration
Slows GIT transit
Modulate NT and hormonal release
Psychomimetic effects

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7
Q

Describe the absorption and distribution of opioids

A

Good absorption SQ, IM and oral
High interpatient variability in first pass effect
Rapidly distributed to highly-perfused organs (brain, kidney, liver, lungs)
Accumulates in fatty tissues

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8
Q

Morphine metabolized to what compounds?

A

M3G - neuroexcitatory (GABA/glycinergic)
M6G - more potent analgesic

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9
Q

Route of elimination of morphine, and effects when impaired

A

Excreted by kidney
Renal failure may lead to M3G-induced seizures
M6G - enhanced opioid effects

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10
Q

Explain metabolism of codeine

A

Metabolized to active compounds by P450 CYP2D6 - demethylation to morphine
Genetic polymorphism linked to variation in analgesic response

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11
Q

MOA of opioids

A

Binds to GPCR that:
1) closes voltage-gated calcium channel on presynaptic terminals, reduces NT release:
- glutamate
- ach
- NE
- seotonin
- substance P

2) open potassium channel - K efflux = hyperpolarised and inhibit post-synaptic neurons and nerve activity

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12
Q

Opioids act on multiple synapses, transmitters and receptors, such as in

A

Inflamed/damaged peipheral tissue
spinal dorsal horn where pain fibers are
Descending inhibitory neurons (periaqueductal grey, rostral ventral medulla)
Release of endogenous ligands

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13
Q

Define tolerance

A

Gradual loss of effectiveness with frequently repeated doses of opioid analgesics
To reporduce original response, larger dose must be given

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14
Q

Mechanism of development of tolerance

A

Concepts:
1) upregulation of secondary messenger system (CAMP)
2) Failure of receptor recycling - normally activation leads to endocytosis followed by resensitisation and recycling of receptor to cell surface
3) Receptor uncoupling: dysfunction of structural interactions between mu receptor, G proteins, 2nd messenger system and target ion channel

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15
Q

CNS effects of opioids

A

analgesia
euphoria
sedation without amnesia
respiratory depression
cough suppression
NV
miosis
temperature dysregulation
trunchal rigidity

no effects on cerebral blood flow and ICP UNLESS resp depression = increase PCo2

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16
Q

Effects of opioids of CVS

A

Bradycardia (except meperidine - antimuscarinic actions = tachy)
Hypotension

17
Q

Effects of opioid on GIT

A

constipation due to actions on enteric and CNS - reduced motility, increased tone
biliary colic

18
Q

Effects of opioid on urinary system and kidneys

A

Urinary retention due to:
increased sphincter and detrusor tone
decreased awareness of bladder stimuli

Renal dysfunction from decreased renal blood flow

19
Q

Other effects of opioids

A

Release of ADH, prolactin, somatotrophin
Pruritus
Modulation of immune system

20
Q

Opioids are part of management plan for what type of pain on the WHO ladder

A

Moderate to severe pain

21
Q

Common errors in analgesic prescription

A

Failure to assess pain severity
Failure to match severity to appropriate level of therapy
Failure to monitor effectiveness and modify plans if response inadequate/excessive
Failure to distinguish between acute and chronic pains - rolerance and physical dependence

22
Q

Clinical uses of opioids

A

Analgesia
Adjuvant analgesia added to less-than-satisfactory opioid regime
Anesthetic

23
Q

What type of pain does opioid works best on

A

Opioid works best on severe constant pain (sharp intermittent less effectively controlled)

24
Q

Pain a/w cancer requires continuous use of potent opioids. How to administer?

A

Fixed interval administration rather than PRN use
Slow release form - longer and more stable level of analgesia
Transdermal patches if GI function prevents oral use
Buccal and nasal prep can be effective

25
Q

Use of opioids in obstetric labour results in

A

neonatal respiratory depression

Safer alternative is meperidine

26
Q

Types of adjuvant analgesiics

A

Multipurpose (antidepressants, corticosteroids, alpha2 adfrenergic, neuroleptics)
Neuroleptic pain (AEDs, LA, NMDA antagonists)
Bone pain (calcitonin, bisphosphonates, radiopharm)
MSK (muscle relaxants)
Painr from bowel obstrction (octreotide, anticholinergics)

27
Q

Clinical use of opioid as anesthetic

A

preop - premed as sedative, anxiolytic, analgesic

intraop - adjuncts to other anesthetic agents

high dose used as primary component of anesthetic regime

regional analgesia by administration into epidural or subarachnoid space to act on spinal cord dorsal horn superficial neurons
epidural has less SE (resp depression, pruritus, NV)
GOOD for post op pain control

28
Q

When does tolerance manifest

A

2-3 weeks of frequent exposure to ordinary therapeutic doses

Develops mores readily in more potent opioids, when large doses given at short intervals

29
Q

Degree of tolerance depends on

A

1) Opioid - more common in mu
Cross tolerance may be partial or incomplete agonists
2) Effects:
- marked tolerance to analgesic, sedative, respi depressant, antidiuretic, emetic and hypotensive effects
tolerance does NOT develop to miotic, convulsant and constipating actions

30
Q

How is tolerance managed

A

Opioid rotation - change to another opioid
Use of adjuvant non-opioid to allow recoupling of opioid receptors
- ketamine shown to reduce post-op pain and opioid requirement in tolerant patients

31
Q

Symptoms of physical dependence

A

rhinorrhea
lacrimation
yawning
hyperthermia
piloerection
hypervenetilation
mydriasis
muscular aches
vomiting
diarrhea
anxiety
hostility

32
Q

Time of onset, intensity and duration of symptoms of physical dependence related to

A

DRUG and half life
morphine/heroin withdrawal starts 6-10h, peaks 36-48h, ends aft 5 days
methadone - less severe but last up to 2 wks

33
Q

Psychological dependence such as?

A

euphoria, sedation, pleasurable sensation promote compulsive use

34
Q

How to minimize risk of tolerance

A
  • establish therapeutic goals before starting opioid
  • limit dosage at lowest effective level (no early refills, no multiple prescrtibers)
  • consider alternative eanalgesics
  • frequently re-evaluate need for opioids
35
Q

Contraindications of opioids

A

1) Combining full agonist (morphine) with partial agonist (pentzocine) = reduce analgesia and induce withdrawal
2) HI - resp depression = cerebral vasodilation = raised ICP
3) Pregnant women - fetus develops dependent, early postpartum w/drawal
4) Avoid/reduce dose in hepatic/renal dysfx
5) Avoid combination with sedative-hypnotics (resp depression)
antipsychotics (sedation, CV effects)
MAOi (hyperpyrexic coma)

35
Q

Contraindications of opioids

A

1) Combining full agonist (morphine) with partial agonist (pentzocine) = reduce analgesia and induce withdrawal
2) HI - resp depression = cerebral vasodilation = raised ICP
3) Pregnant women - fetus develops dependent, early postpartum w/drawal

CA1 (3 decks)

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