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Semester 4 - Clinical Pharmacology And Therapeutics > Opiods > Flashcards

Opiods Flashcards

1
Q

What is nociception?

A

Non-conscious neural traffic due to trauma or potential trauma to tissue

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2
Q

What is pain?

A

Complex, unpleasant awareness of sensation modified by experience, expectation, immediate context and culture.

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3
Q

How do you feel pain?

A
  1. Nociceptors stimulated
  2. Release of substance P and glutamate.
  3. Afferent nerve stimulated
  4. Fibres decussate
  5. Action potential ascends
  6. Synapses in thalamus
  7. Project to post central gyrus
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4
Q

How can we modulate pain?

A

Have modulators in peripheral system and in central system.

Peripherally: Substantia Gelatinosa

Centrally: Peri-aqueductal grey

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5
Q

How can we modulate pain peripherally?

A

Tissue damage then through Ad and C fibres to the substantia gelatonosa then up spinothalamic tract to the thalamus.

Also, if we ‘rub it better’ it stimulates the Ab fibres which simulate the lamina and cause inhibition of Ad and C fibres.

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6
Q

How do we modulate pain centrally?

A

Pain acting on thalamus and cortex stimulate the Periaqueductal grey matter.

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7
Q

MOP

A

Supraspinal / GI tract

Decreased cAMP

Outward flux of potassium

Hyperpolarisation and decrease Substance P release

Enkephalins and B-endorphins

Analgesia, depression, euphoria, dependence, respiratory sedation

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8
Q

DOP

A

Wide distribution

Decreased cAMP

Influx of Ca

Hyperpolarisation and decrease of substance P release

Enkephalins

Analgesia, inhibit dopamine, modulate u

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9
Q

KOP

A

Spinal cord / Brain / Periphery

Decreased cAMP

Efflux of potassium, Influx of calcium.

Hyperpolarisation and decrease substance P release.

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10
Q

Describe the WHO analgesic ladder

A

Simple analgesia e.g. paracetamol / NSAIDs

Weak opioid e.g Codeine

Strong opioid e.g. Morphine, fentanyl

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11
Q

What do you take for arthritic pain?

A

NSAIDS

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12
Q

What do you take for neuropathic pain?

A

Anticonvulsants
Tricyclics
SSRIs
SNARIs

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13
Q

Describe the opiods as a class

A

Exploit natural opioid receptors either agonise or antagonise

Main therapeutic effects via u-receptors

Aim to modulate pain

Also indicate in cough, diarrhoea, palliation

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14
Q

How can you give morphine?

A

PO, IV, IM, SC, PR

But, gut absorption can be erratic

Significant first pass effect - 40% oral bioavailability.

IV and SC tend to be better.

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15
Q

Describe distribution, metabolism and elimination of morphine

A

Distribution: Rapidly enters all tissues including foetal
Struggle to cross blood-brain barrier.

Metabolism: Morphine + glucuronic acid - M6G + M3G

Eliminated renally.

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16
Q

On what receptors does morphine mostly act?

A

U (MOP) receptors - complete activation of u.

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17
Q

How does morphine work?

A

Analgesia

Euphoria

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18
Q

What are the side effects of morphine?

A

Respiratory Depression - medullary resp centre less responsive to CO2.

Emesis - stimulate CTZ

GI tract - decrease motility, increasing sphincter tone

Cardiovascular

Miosis

Histamine release - careful with asthmatics.

19
Q

Describe the absorption, distribution, metabolism and elimination of Fentanyl

A

Absorption: IV, epidural, Intrathecal, Nasal

Distribution: Highly lipophilic, highly protein bound, high level of CNS crossing

Metabolism: Hepatic via CYP3A4

Elimination: Half life 6 minutes, renally excreted

20
Q

How is fentanl different to morphine?

A

100% potency - MUCH more potent

Higher affinity fo u receptor.

21
Q

Actions of fentanyl

A

Analgesia

Anaesthetic

22
Q

What are the side effects of fentanyl?

A

Respiratory distress
Constipation
Vomitting

23
Q

Describe the absorption, metabolism and elimination of codeine

A

Absorption: PO, SC administration

Metabolism: Codeine to morphine via CYP2D6. This enzyme has extremely variable expression. CYP2D6 inhibited by fluoxetine.

Elimination: Glucoronidation of morphine and renal excretion

24
Q

How potent is codeine compared to morphine?

A

Approx 1/10th potency

25
Q

Describe the actions of codeine

A

Mild to moderate analgesia

Cough depressant

26
Q

What are the side effects of codeine?

A

Constipation

Respiratory depression - worse in children

27
Q

Describe absorption, metabolism and elimination of Buprenorphine

A

Absorption: Transdermal, Buccal, Sublingual

Distribution: Very lipophilicity

Metabolism: Hepatic via CYP3A3 then glucoronidation before biliary excretion.

Elimination: Biliary > Renal
Safe in renal impairment
Half life 37 hours.

28
Q

How does buprenorphine compare to morphine?

A 
Very high affinity for u receptor. 
Low Kd. 
Long duration of action 
Not easily displaced 
Lower Emax as partial agonist, lower efficacy 
Antagonist at k receptors.
29
Q

What can you use buprenorphine for?

A

Moderate to severe pain

Opioid addiction treatment

30
Q

What are the side effects of buprenorphine?

A

Respiratory depression
Low Bp
Nausea
Dizziness

31
Q

Describe the absorption, metabolism and elimination of Naloxone

A

Absorption: IV, IM, Intranasal, PO
Very low oral bioavailability as extensive first pass effect
Rapid onset of action

Distribution:
Rapid distribution as very lipophilic

Metabolism: Hepatic - naloxone-3-glucuronide
Renal excreted

Elimination: Duration of action 30-60mins

32
Q

How does naloxone compare to morphine?

A

Affinity u>d>k

Greased affinity than morphine

Affinity less than buprenorphine

33
Q

What are the actions of naloxone?

A

Competitive antagonism of opioids.

34
Q

What are the side effects of naloxone?

A

Short half life

Slow infusion

35
Q

Describe how opioid tolerance occurs

A

Up-regulate by making more receptors so synthetic bind and endogenous no longer cause a response.

36
Q

What do you use for opioid withdrawal?

A

Methadone - reduced E(max) and reduced side effects

37
Q

Why is overdose a growing problem?

A

As abusing drugs prescribes and abusing drugs need as not got opioids anymore.

Prescribe short courses a much as you can.

38
Q

Describe an overdose of opioids

A

u receptor
Variable effects of doses
Respiratory depression most common cause of death
Can decrease effects - d agonist, 5HT4 agonists

Naloxone infusion as treatment.

39
Q

What symptoms do you get in an overdose of opioids?

A 
Dependace 
Vomiting
Constipation
Hypotension and bradycardia 
Decreased sex drive 
Histamine release 
Miosis 
Drowsiness 
Respiratory depression 
Apnoea
40
Q

What groups of patients require special consideration?

A 
Manual labourers / drivers 
Elderly 
Bedbound 
Asthmatics 
Biliary tract obstruction 
Respiratory disease 
Renal impairment 
Pregnancy
41
Q

In who are opioids completely contraindicated?

A 
Hepatic failure 
Acute respiratory distress 
Comatose 
Head injury - as already disrupt blood brain barrier 
Raised ICP
42
Q

How do you prescribe opioids in palliative prescribing>

A

Difficult as Harold Shipman
Tend to ignore special considerations
Indications: Pain, Shortness of breath
Manage side effects: Nausea, constipation

43
Q

What do opioids prescriptions have to include?

A

Date and prescribers address and full name.
Patient address and name
Form of the drug - tablets, syrup, capsules, catches, ampoules ect.
Units - mg, mls, ect.
Total volume - words and figures
Clearly defined doses.

44
Q

Why are opioids controlled under the misuse of drugs legislations?

A

Aim to prevent:
Misuse
Illegal obtainment
Harm being caused

Semester 4 - Clinical Pharmacology And Therapeutics (26 decks)

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