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MBCHB3: Nervous system module. > Lecture 25: Analgesic drugs 1 > Flashcards

Lecture 25: Analgesic drugs 1 Flashcards

1
Q

What are narcotic analgesics?

A

Analgesics that cause narcosis:

  • > Narcosis
  • > Impaired consciousness
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2
Q

What are the types of pain after injury?

A

Surgical trauma:
- Nocioceptive pain
- Inflammatory pain
= Opioids/opiates sensitive

Neuropathic pain (not sensitive)

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3
Q

What are routes of administration?

A 
Oral
Parenteral (jab)
Transmucosal
Transdermal
Nasal
Sublingual
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4
Q

What is opium?

A

Opium is the dried latex from opium poppies containing:

  • Narcotic alkaloids
  • Non-narcotic alkaloids
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5
Q

What is narcotic alkaloids used to create?

A

Morphine

Codiene

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6
Q

What are non-narcotic alkaloids used for?

A

Papaverine
Thebaine
Noscapine

Dont need to know this

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7
Q

What are opiates vs opiods?

A

Opiates = Natural

Opioids = Chemically synthesised

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8
Q

Describe the opioid receptor;

A

Opioid receptors are essentially pre-synaptic, belong to the G protein coupled family of receptors (GPCRs)

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9
Q

Describe the mechanism of action of opioid receptors:

A
  1. Activated Gi proteins -> Inhibition of adenylate cyclase enzyme -> Decreased Ca channels permeability (-> Blocked transmitter release)
  2. Increased K conductance -> Hyperpolarization of post synaptic neuron -> Decreased response
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10
Q

What are the different types of opioid receptor?

A

Mu
Kappa
Delta

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11
Q

What are Mu receptors found?

A

Spinal cord
Brainstem (peri-aqueductal grey)
Thalamus
Cortex

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12
Q

Where are kappa receptors found?

A

Limbic system
Hypothalamus
Brainstem (peri-aquaductal grey)
Spinal cord

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13
Q

Where are delta receptors found?

A 
Olfactory bulb
Cerebral cortex
Nucleus accumbens
Amygdala
Pontine nucleus
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14
Q

Are opioids primarily central?

A

There is evidence to suggest after tissue damage opioids can act on peripheral nociceptor terminals.

These opioid receptors are synthesised in the cell body (DRG) and transported towards the periphery.

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15
Q

What are some opioid agonists and what are there actions?.

A

Morphine, Fentanyl, Pethide

Activation of all receptor subclasses though with varying affinitites

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16
Q

What are some opioid antagonists, what are their actions?

A

Naloxone, Naltrexone

Devoid of activity in all receptor classes

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17
Q

What are some opioid agonist-antagonist, what are their actions?

A

Nalorphine, Petazocine

Agonist activity one one type and antagonist on other receptors

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18
Q

What are some partial agonists, what are their actions?

A

Bup-re-norphine

Activity at one or more, but not all receptor types

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19
Q

What are the adverse effects of opioids?

A
  • Resp. depression
  • Somnolence (drowsiness)
  • Dizziness
  • Constipation
  • Ileus
  • Itching
  • Nausea and vomiting
  • Vagally mediated bradycardia
  • Hypotension (morphine)
20
Q

What are the precautions for opioid use?

A
  • Sleep apnea
  • COPD (chronic hypocapnic)
  • Elderly
21
Q

What are natural opioids?

A

Morphine

Codiene

22
Q

What are semi-synthetic opioids?

A

Bup-re-norphine
Oxycodone
Di-acetyl-morphine (dimoprhine) (Heroin)

23
Q

What are some fully synthetic opioids?

A

Fentanyl
Pithidine
Methadone
Tramadol

24
Q

What are some endogenous opioid peptides?

A

Endorphins
Endomorphins
Enkephalins
Dynorphins

25
Q

What are some notes for using opioids?

A
  • To be administered through the most effective and comfortable route
  • Round the clock for severe to moderate pain
  • Consider inter-patient variability
  • Use of adjuvants for enhancing opioids analgesia and reducing side effects i.e NSAIDS
26
Q

What are the two main effects of opioids?

A

Analgesia
Euphoria

It is the euphoric effect that can lead to abuse

27
Q

What are the adverse conditions of opioid use?

A
  • Physical dependence i.e not addicted, withdrawl symptoms.
  • Psychological/emotional dependence (cravings)
  • Drug tolerance (consider opioid rotation), larger doses required to achieve the same effect
  • Opioid addiction (addiction is a disease, compulsive use despite harm)
28
Q

What are the symptoms of opioid withdrawl?

A

Mostly autonomic

  • Altered HR
  • Altered BP
  • Altered RR
  • GI, Nausea, vomiting, cramps, diarrhoea
  • Sweating

-> Irritability, restlessness, tremor, yawning

29
Q

How do you manage opioid withdraw?

A
  • > Give methadone or bup-re-norphine (cross tolerance, then slowly withdraw)
  • > Clonidine, reduce ANS symptoms
  • > Promethazine for N&V
  • > Diazepam (for muscle cramps)
  • > Anti-diarrheal
30
Q

How is rapid opiate detox done? ~6hrs

A
  • Under GA pt not subject to withdraw discomfort
  • High doses of nal tre xone used
  • Oral dose can be continued to reduce the risk of relapse
31
Q

Give the relative potencies of some opioids:

A

Fentanyl is 50-100x more potent than Morphine

32
Q

What are the pharmacokinetics of morphine?

A
  • Low lipid solubility (Slower onset and longer duration)
  • 1/3 bound to plasma proteins
  • Large VoD
33
Q

What are the routes of administration for morphine?

A

Oral (Bioavailability ~25%)

IV, IM, Epidural

34
Q

What is the metabolism of morphine?

A

Liver

  • > 70% to Morphine-3-glucuronide
  • > Morphine-6-glucuronide (half as potent, longer half life)
35
Q

Write some notes on pethidine:

A

Pethidine

  • > Converted to norpethidine (active form)
  • > 8-12hr half life

NB: Can accumulate in renal failure-> Hallucination, Seizures

Can interact with anti-depressants
- Coma, convulsions, labile circulation, hyperpyrexia

36
Q

Write some notes on Fentanyl:

A
  • Stronger Mu receptor agonist
  • 80-100 times more potent
  • Predominantly metabolised in the liver to nor-fentanyl which is inactive
  • Excreted in liver over days
37
Q

How is fentanyl administerd?

A

IV most common

Can do transdermal patches but

  • Slow onset
  • Inability to rapidly change doses

Transmucosal lozenges
Nasal and sublingual spray
sublingual tablets

38
Q

Describe fentanyl HCl ionto-phoretic transdermal system:

A

Iontophoresis is a method of transdermal PCA administration of ionizable drugs in which the electrically charged components are propelled through the skin by an external electric field

39
Q

Write some notes on methadone:

A

Oral: Bioavailability 70%, can be administered in other ways

  • No significant cognitive impairments
  • No euphoria
  • Safe in renal and liver failure
40
Q

What is methadone used for?

A

For chronic pain patients (Due to its NMDA antagonsim)
For neuropathic pain
For opioid withdrawal
For detox

41
Q

Write some notes on tramadol:

A
  • Oral bioavailability greater than 70%

- Inhibits uptake of noradrenaline and serotonin

42
Q

Whats a risk specific to tramamdol?

A

May causes serotonin syndrome if administered with SSRI antidepressants

43
Q

What are some consideration for codiene?

A

Codeine is metabolised to morphine by Cytochrome P450

Ultra rapid metabolisers are at higher risk of toxic opioid effects

Slow metabolisers may not experience adequate analgesic effect with codeine

44
Q

What are opioid antagonists?

A

Naloxone
Nal tre xone

Devoid of all activity

45
Q

What are coanalgesics and some examples?

A
  • Shown to enhance the analgesic effect, but devoid of analgesic function
    i. e
Tricyclic antidepressants
Anticonvulsants i.e gabapentin
Anxiolytics
Corticosteroids
Others i.e Ketamine, clonidine

MBCHB3: Nervous system module. (39 decks)

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