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308: Clinical pharmacology and therapeutics > Analgesia > Flashcards

Analgesia Flashcards

1
Q

Inflammatory pain

  • Presentation
  • Indicated analagesia
A

Presents

  • Throbbing, aching
  • Localised area

Drugs

  • NSAID
  • Paracetamol
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2
Q

Nociceptive/ somatic

  • Presentation
  • Causes
  • Indicated analgesia
A

Sharp pain, localised
- Caused by activation of nociceptors in skin, muscles, bone

Drugs

  • NSAIDs
  • Paracetamol
  • Opioids
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3
Q

Nociceptive- visceral

  • Presentation
  • Cause
  • Indicated analgesia
A

Deep, aching
Poorly localised
Cramping
- Caused by activation of nociceptors from stretching, distension or inflammation

Drugs

  • NSAIDs
  • Paracetamol
  • Opioids
  • Neuropathic agents
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4
Q

Neuropathic

  • Presentation
  • Cause
  • Indicated analgesia
A

Shooring, burning, hypersensitive

Tingling, numbing

Caused by direct damage to PNS/CNS

Drugs
- Neuropathic agents

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5
Q

Analgesics classifications

A

Simple

  • NSAIDs
  • Paracetamol

Opioids

Neuropathic agents

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6
Q

Paracetamol

- Dose

A

Normal dose
- 1g QDS

Liver impairment/ <50kg
- 500 mg QDS (max 15mg/kg IV)

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7
Q

NSAIDs

- Dosing

A

Ibuprofen
- 400mg TDS PO

Naproxen
- 250-500mg BD PO

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8
Q

NSAIDs side effects

A

GI bleeds/ Side effects

Nephrotoxic

  • Decreases blood flow
  • Na+ and water retension

Reyes syndrom

Drug interactions

  • Warfarin
  • Methotrexate
  • Lithium

Asthma sensitivity

Prescribe PPI for preventative protection
- Lansoprazole 15mg OD

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9
Q

Weak opioids

  • Indication
  • Examples
  • Metabolism
A

Indication

  • Moderate pain
  • Anti-diarrhoeal

Examples

  • Codeine
  • Hydromorphine (first line)

Metabolism

  • Pro-drugs, have to be converted to morphine (codeine) or dihydromorphine (hydromorphine)
  • Not metabolised in 1 in 10 caucasians or have ultrametabolisers
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10
Q

Weak opioids

- Doses

A

Codeine
- 30-60mg QDS

Dihydrocodeine
- 30mg every 4-6 hours.

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11
Q

Strong opioids

  • Indication
  • Examples
  • Metabolism
A 
Examples
- Morphine
- Oxycodone
- Fentanyl--> patch more suitable for prolonged pain.
Good for renal impariment patients
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12
Q

Strong opioids doses

  • Morphine
  • Oxycodone
A

Morphine
Naive- 5-20mg 1-2 hrs PRN
- Elderly= 2.5-10mg 2-4 hrs
- Renal impairment= 2.5-5mg. Not used if eGFR<30

Oxycodone
Naive- 5-10mg 2-4 hrs

Elderly= 1.25-5mg

Renal impairment
- 1.25-2.5mg

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13
Q

Opioid dose equivalents

A

Morphine IV/IM= 2x oral

Diamorphine s.c= 3x morphine oral

Oxycodone oral= x2 morphine oral

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14
Q

Nefopam

  • Drug type
  • Dose
  • Side effects/ contraindications
A

Drug type

  • Non-opioid/ NSAIDs
  • Good alternative for opioid dependent patients.

Dose
- 60 mg TDS (30 in elderly)

Side effects

  • Nausea
  • Dizziness
  • Urinary retention
  • Dry mouth
  • Pink urine
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15
Q

Ascending pain pathway

A

Spinothalamic tract:

  1. Nociceptors at site of tissue (somatic/ visceral)
  2. A-delta fibres transmits sharp, localised pain quickly.
    - C fibers transmits dull, burning pain slowly
  3. First order neurones synapses with second order neurones at dorsal horn
  4. Second order neurones cross spinal cord and ascending the anterior column to thalamus
  5. Third order neurones synapse from thalamus into somatosensory cortex.
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16
Q

Descending modulation of pain

  • receptors
  • Endogenous opioids
  • Pain control centres
A

3 types of opiod receptors

  • Mu, kappa, delta
  • when activated, they hyperpolarised neurones and reduces their excitibility

Endogenous opioids activate opioid receptors

  • Β-endorphins = mu opioid receptors
  • Dynorphins = kappa opioid receptors
  • Enkephalins = delta opioid receptors

Periaqueductal grey matter (PAG) in midbrain and rostral ventral medulla (RVM)

  • Contains high levels of opioid receptors
  • Descending fibres from PAG and RVM synapse with spinothalamic tract at dorsal horn via 5HT/NA neurone
  • Inhibits communication between 1st and 2nd order neurone
17
Q

WHO analgesia ladder

A
  1. Non-opioid +/- adjuvant
    - NSAIDs, paracetamol
  2. Add weak opioid
    - Tramadol, codeine, dihydrocodeine
  3. Replace weak opioid with strong opioid
    - Morphine
    - Oxycodone
    - Fentanyl
    - Diamorphine
    - Alfentanil
    - Hydromorphone
18
Q

Pharmacological adjuvants

A

Corticosteroids

antidepressants

  • Duloxetine
  • Amitriptylline
  • Mirtazepine

Antimuscarinics

Benzos

Ketammine

Bisphosphonates

Antiepileptics

  • Gabapentin
  • Pregaballin
19
Q

Pharmacological effects of opioids

- Examples of use specific to effect

A

Analgesia
- Inhibition of spinothalamic tract

Psychotrophic
- Anxiolytic and euphoria

Respiratory depression

  • Acts on respiratory centre in medulla
  • Oramorph can be used in end stage COPD pts SOB

Suppresses cough reflex
- Codeine can be used for cough

Constipation

  • Delays gastric emptying
  • Inhibits peristalsis
  • Codeine can be used for high output stoma.
20
Q

Pharmacological adverse effects of opioids (5)

- Ways of overcome/ relieve adverse effects

A

Constipation

  • Change medication or ad laxative
  • Consider peripherally acting opioid antagonist in severe caes (naloxogel)

Nausea and vomiting
- Anti-emetic

Sedation
- Advice of this

Drug mouth

  • Sugar free chewing gum
  • Mouthwash

Pruritus
- Antihistamine

21
Q

Symptoms of opioid toxicity

A

Drowsiness

Miosis
- Pinpoint pupils

Respiratory depression

Confusion, agitation

Hallucinations

Myoclonic jerks

22
Q

Management of opioid toxicity

- Mild/ moderate

A

Mild-moderate

  • Reduce/ stop drug
  • Check renal + hepatic function
  • Ensure adequate hydration

Severe (RR<8, decreased O2, unresponsive)
- Naloxone

23
Q

Codeine

  • Action
  • dose
  • Major side effect
  • Morphine equivalence
A

Action
- Mu receptor

Dose

  • 15-60mg PO QDS
  • 240mg Max in a day

Major side effect
- Constipation

Morphine equivalence
- /10

24
Q

Dihydrocodeine

  • Action
  • dose
  • Major side effect
  • Morphine equivalence
A

Action

  • Semi-synthetic analogue of codeine
  • Acts on Mu

Dose

  • Same as codeine
  • 15-60 PO QDS

Major side effect
- Constipation

Morphine equivalent= /10.

25
Q

Tramadol

  • Action
  • dose
  • Major side effect, cautions
  • Morphine equivalence
A

Action

  • Acts on Mu
  • Monoaminergic

Dose
- 50-100 PO QDS

Major side effect

  • Nausea and vomiting
  • Sedation

Caution

  • Elderly
  • MAOIs
  • Seizures

Morphine equivalent= /5-10

26
Q

Morphine

  • Action, metabolism and excretion
  • Perparations
  • dose
  • Major side effect, cautions
  • Morphine equivalence
A

Action

  • Acts on Mu and Kappa
  • Metabolised in liver, excreted in urine

Preparation

  • Immediate release: oramorph, sevredol
  • Modified: MST, Zomorph

Dose
- 50-100 PO QDS

Major side effect

  • Nausea and vomiting
  • Sedation

Caution

  • Elderly
  • MAOIs
  • Seizures

Morphine equivalent= /5-10

27
Q

Morphine preparations

  • Immediate and slow release
  • Time of onset, time of peak
  • Half life
  • Duration of action
A

Immediate release

  • Acts in 15-30mins
  • Peaks 30mins-1hr
  • Half life= 2-4hrs
  • Acts for 4 hrs

Slow release

  • Onset= 2 hours
  • Peak= 3-4hrs
  • Half life- 2-4hrs
  • Duration= 12 hrs
28
Q

Oxycodone

  • Action
  • Metabolism
  • Preparations
A

Semi-synthetic opioid

  • Full opioid agonist
  • Metabolised in liver

Preparations

  • IR:
  • Modified release:
29
Q

Hydromorphone/ Palladone

  • Action
  • Metabolism
  • Preparations
A

Similar to morphine

  • Selective Mu agonism
  • metabolised in liver
  • Caution in renal impairment

Immediate and modified release preparations

30
Q

Fentanyl

- Administration

A

Patches

  • Remains in skin 24 hrs post removal
  • Not suitable for unstale/ rapidly escalating pain

Lozenges/ SL/ Intranasal
- Rapid onset, shorter duration

31
Q

Alfentanil

  • Action
  • Metabolism
  • Administration
A

Potent, short acting synthetic opioid (fentanyl)

  • Third line opioid use
  • Half life= 30mins
  • metabolise in liver= clearance reduced in liver impairment, elderly.

Administration

  • Injectable
  • Can be used when eGFR< 30ml/min
32
Q

Breakthrough dose

A

Breakthrough pain is sudden flare of acute pain from normal, background pain

Breakthrough analgesia helps to relieve that pain

308: Clinical pharmacology and therapeutics (13 decks)

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