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Pharmacology Term 6 > 8.1- Opioids > Flashcards

8.1- Opioids Flashcards

1
Q

Define nociception

A

non-conscious neural traffic in response to potential trauma

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2
Q

Define pain

A

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

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3
Q

Define nociceptive pain

A

pain caused by an inflammatory or non-inflammatory response to an overt or potentially tissue- damaging physical stimulus

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4
Q

Define neuropathic pain

A

pain caused by a lesion or disease of the somatosensory nervous system ( ie to the actual neurone itself )

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5
Q

Name 5 types of analgesia

A
  • Paracetamol
  • NSAIDs
  • Opioids
  • Adjuvants
  • Placebo
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6
Q

What would you give as step 1 on the WHO analgesia ladder? ie MILD PAIN

A

give a NON-OPIOID +/- adjuvant

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7
Q

What would you give on step 2 on the WHO analgesia ladder? ie MODERATE PAIN

A

-give a WEAK OPIOID
+/- non opioid
+/- adjuvant

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8
Q

What would you give on step 3 on the WHO analgesia ladder? ie SEVERE PAIN

A

give a STRONG OPIOID
+/- non opined
+/- adjuvant

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9
Q

Give 3 examples of a non-opioid

A

ibuprofen
other NSAID
Paracetamol
aspirin

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10
Q

Give 3 examples of WEAK OPIOIDS

A

codeine
tramadol
low-dose morphine

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11
Q

Give 4 examples of STRONG OPIOIDS

A 
morphine 
fentanyl
oxycodone 
hydromorphone 
buprenorphine
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12
Q

What are some adjuvants for pain?

A 
antidepressants 
anticonvulsants 
antispasmodic 
muscle relaxant 
bisphosphonate
corticosteroid
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13
Q

What are the primary sensory afferent neurones of pain?

A

Adelta or C fibres

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14
Q

Between which 2 neurones does pain transmission occur?

A

between primary afferent sensory neurone and secondary relay neurone ie synapse of substance P

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15
Q

Where do the primary and secondary neurones synapse?

A

SUBSTANTIA GELATINOSA in the dorsal horn of the spinal cord

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16
Q

Where does inhibition of this pain transmission come from?

A

1) Inhibitory interneurones linked to Adelta and Abeta fibres, inhibiting synapse between primary and secondary neurones
2) inhibitory descending pathways from higher centres of the brain

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17
Q

Where are descending analgesia producing pathways located in the brain?

A

Periaqueductal Grey Matter ( PAG) in the midbrain

projects to Dorsal horn of spinal cord

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18
Q

Describe the central modulation of pain

A
  • PAG sends signals to RVM and carried down medial pathways to serotonergic and Noradrenergic neurones
  • Serotoneric and noradrenergic neurones are stimulated and release Serotonin and NA into spinal cord
  • –> activate inhibitory interneurones which
  • -> release ENDOGENOUS OPIOIDS binding to opioid receptors–> inhibit substance P release to secondary neurones going up ascending pathways
19
Q

DEFINE:
A) Opiate
B) Opioid

A

a) Opiate: any agent derived from opium. ( alkaloid mixture from poppy seeds)
b) OPIOID: substances ( exogenous or endogenous ) with morphine-like properties
- act primarily in the SPINAL CORD and brain to inhibit transmission of pain

20
Q

How do opioid work?

A

bind to specific opioid receptors in the CNS to mimic the endogenous peptide neurotransmitters

21
Q

what are the endogenous opioids released by the inhibitory interneurone?

A

Enkephalins
B-endorphins
Dynorphins

22
Q

Name:
2 natural opioids
3 semisynthetic opioids
3 synthetic opioids

A

NATURAL: morphine, codeine
SEMIsynthetic: hydrocodone, hydromorphone, oxycodone, oxymorphone, Buprenorphine
SYNTHETIC: fentanyl, tramadol, methadone

23
Q

Describe the opioid receptors

A
  • G protein coupled receptors
  • Coupled to Gi; inhibitory G-protein subtype
  • located pre AND post synaptically
24
Q

Name the 4 types of opioid receptors

A

μ mu opioid receptor- most important
δ delta opioid receptor
K kappa opioid receptor
ORL1 ( Opioid receptor like 1 (NOP)

25
Q

Describe opioid action PRE-SYNAPTIC

A

Gαβγi → Gαi + Gβγi
• Gβγi inhibits voltage operated Ca2+ channels (VOCC)
• Reduced Ca2+ → less neurotransmitter release of substance P going to ascending pathways

26
Q

Describe opioid action POST-SYNAPTIC

A

Gαβγi → Gαi + Gβγi
• Gβγi opens K+ channels
• K+ efflux→ hyperpolarises the cells and makes them less excitable

27
Q

Give an example of:

a) An opioid agonist
b) A partial opioid agonist
c) An opioid antagonist

A

a) MORPHINE
b) BUPRENORPHINE
c) NALOXONE

28
Q

Give 3 uses of an opioid antagonist

A
  • treats opioid toxicity
  • reverses respiratory depression
  • treatment for opioid dependence
29
Q

Which opioid antagonist is commonly used?

A

NALOXONE
always prescribe with morphine to save time in an emergency
half life of 1-1.5 hrs

30
Q

Give some routes of morphine admin

A 
IV
PO
IM 
SC
nebulized
rectal
epidural
31
Q

Which route is the most preferred

A

IV

  • gives the most rapid response
  • AVOIDS hepatic first pass metabolism
  • often used for severe pain w intrathecal route
  • patient controls the level of analgesia directly (PCA)
32
Q

Describe the oral pharmacokinetics of morphine

A

-well absorbed from gut
-undergoes EXTENSIVE first pass metabolism w a 25% oral bioavailability
normally its half life is 2 hours

33
Q

What are the two metabolites of morphine (orally)?

A

morphine-6-glucoronide

morphine-3-glucoronide

34
Q

What is the danger of morphine given orally and what condition is it avoided in?

A

morphine normally has a half life of 2 hrs, BUT one of its metabolites, Morphine-6-glucoronide is pharmacologically equivalent to morphine and has a half life of 4-5 hours

this EXTENDS the period of effective analgesia

Avoided in hepatic and renal failure as they can impair morphine excretion and increase half lives up to 50 hrs–> can cause morphine toxicity and terminal organ failure

35
Q

What would you give methadone for and why?

A

suitable for treating chronic pain rather than post-op pain

-has a half life of 24 hours

36
Q

What is the special case of codeine pharmacokinetics?

A

Codeine has to be metabolised to morphine by CYP2D6 in order to become pharmacologically active

BUT CYP2D6 polymorphisms (genetic) are present in some Caucasian populations therefore they cannot effectively convert codeine to morphine
therefore no analgesia achieved in these populations

37
Q

Name 4 desirable pharmacological effects of morphine?

A
  • Effective analgesia: At spinal and supraspinal level
  • Sedation & Euphoria: By effect on midbrain dopaminergic, serotoninergic and noradrenergic nuclei
  • Effect on bowel movements: Decrease in motility, increase smooth muscle tone
  • Depression of cough reflex: Codeine and morphine have antitussive properties
38
Q

Give a clinical use for each drug:

a) Morphine
b) Diamorphine
c) Methadone
d) Tramadol
e) Tapendatol

A

a) analgesic in terminal illness ( ADR is diarrhoea)
b) analgesic in terminal illness ( unlicensed epidural analgesic)
c) maintenance in dependence
d) analgesic ( 5-HT and NA effects)
e) Analgesic ( specific mu agonist, NA reuptake inhibitor

39
Q

What opioid is given in labour as analgesia?

A

PETHIDINE
given IM
for convulsions
as a norpethidine metabolite

40
Q

Name some undesirable side effects of opioids? (10)

A 
Respiratory depression 
Nausea, vomiting 
Smooth muscle spasm 
Hallucinations 
Pruritis 
Bradycardia 
Hypotension 
Miosis 
Drowsiness 
Dysphoria ( if no pain, morphine can cause restlessness,  unhappiness and agitation
41
Q

Why would you get dependence and tolerance on opioid drugs?

A

down regulation of opioid receptors or decreased production of endogenous opioids

body becomes more tolerant to drug therefore increased dose needed for desired effect

42
Q

How should prescriptions for controlled drugs be written?

A
  • INDELIBLE
  • signed by PRESCRIBER
  • DATED
  • contain PRESCRIBER’S ADDRESS
43
Q

What points should a prescription of a controlled drug ALWAYS state?

A

• the name and address of the patient
• the form (and where appropriate the strength) of the preparation;
• for liquids, the total volume in millilitres (in both words and figures) to be supplied;
• for dosage units, the number (in both words and figures) to be supplied;
• in any other case, the total quantity (in both words and figures) to be
supplied;
• the dose

Pharmacology Term 6 (10 decks)

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