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Nervous system > Opioids > Flashcards

Opioids Flashcards

1
Q

What is nociception ?

A

Non- conscious neural traffic due to trauma 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 variable experiences , context, etc.

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3
Q

how is pain generated ?

A

Via Spinothalmic tract:

  1. Nociceptors stimulated
  2. Release of sub P and glutamate
  3. afferent nerves stimulated
  4. fibres decussate
  5. AP ascends and synapse in thalamus
  6. project to Post central gyrus
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4
Q

what modulates pain peripherally ?

A

Substantia gelantinosa- dorsal horn

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5
Q

what modulates pain centrally ?

A

peri adueductal grey

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6
Q

what do A(delta) and c fibres ?

A

send stimulatory signals up from nociceptors the spinothalmic tract
inhibit the Substantia gelantinosa

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7
Q

how does rubbing your knee help reduce pain ?

A

stimulate AlphaBeta fibres which stimulates substantia geletanosa to modulate the pain from A(delta) and C nerves to reduce signals of pain

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8
Q

how do when modulate pain centrally ?

A

Cortex usually inhibits peri aqueductal Grey matter . During pain , thalamus and cortex send stimulatory signals to PAGM which inhibits spinal cord to reduce pain signals via 5-HT and endogenous opioids

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9
Q

Name the endogenous opioids

A

Enkephalins
Dynorphins
B endorphins

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10
Q

what are the 3 Opioid receptors ?

A 
Mop = mu
DOP= delta
KOP= kappa
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11
Q

outline how opioid receptors work

A

Hyperpolarisation and decrease of substance P

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12
Q

what does Mop receptors modulate ?

A

analgesia , depression , euphoria , dependence , respiratory sedation

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13
Q

Whta do Dop receptors modulate ?

A

analgesia, inhibit dopamine, modulate Mop

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14
Q

what do Kop receptors modulate ?

A

analgesia , duiresis , dysphoria

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15
Q

what is the order of WHO analgesic ladder ?

A

Simple analgesia
weak opioid = codeine
strong Opioid

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16
Q

what should you use for neuropathic pain e.g diabetic neuropathy ?

A

Anticonvulsants
tricyclics
SSRIs, NARI

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17
Q

what other indications can you use opioids ? what receptor is the main one affected ?

A

cough , diarrhoea and palliation

Mop

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18
Q

what is the absorption of morphine ? bioavailibilty ?

A

PO, IV, IM , SC, PR
Gut absorption erratic-
40%

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19
Q

what is the distribution of morphine ?

elimination ?

A

rapidly enters all tissues including foetal
struggles to enter BBB
Renally

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20
Q

what is the metabolism of morphine ?

what molecules

A

significant first pass effect

combines with glucuronic acid –> M6G (Analesgic) and M3G (Neuro stimulatory and irritabilty )

21
Q

what is the MOA of morphine and what is its actions ?

A

Strong affinity to Mop and less so Dop and Kop

Analgesia and Euphoria

22
Q

what are Respiratory side effects of morphine and how do they occur ?

A

resp depression

medullar resp centre less responsive to CO2

23
Q

what are GI side effects of morphine and how do they occur ?

A

Emesis - stimulate chemoreceptor trigger zone decrease motility and increase sphincter tone = constipation , nausea

24
Q

what other side effects are seen in morphine ?

A

Miosis

Histamine- be careful in asthmatics

25
Q

what is the Absorption of fentanyl ?

A

IV, Epidural, Intrathecal , Nasal

80-100% bioavail

26
Q

What is the distribution if fentanyl like ?

A

highly lipophilic , highly protein bound and CNS crossing high

27
Q

What is the metabolism and Elimination like in fentanyl ?

A

Met = CYP3A4

Renally excreted

28
Q

What are features of fentanyl compared to morphine ?

A

100x more potent
high affinity for Mop
less histamine , sedation and constipation

29
Q

what are side effects of Fentanyl ?

A

resp depression
Constipation
vomiting

30
Q

what enzyme metabolises Codeine ? what inhibits said enzyme ?

A

CYP2D6

Fluoxetine , SSRIs

31
Q

how is codeine eliminated ?

A

glucoronidation and renal exertion

32
Q

what is codeine metabolised to ?

A

Codein to morphine via CYP2D6

33
Q

what are the actions of codiene?

A

Cough depressant

Mild/mod analgesia

34
Q

what are side effects of morphine ?

A

Constipation

resp depression - esp in children , dont give under 12

35
Q

what is the pharmokinetics of Buprenorphine ? ADME

A

A- Transdermal
D- Very lipophilic
M- Via CYP3A4
E- Biliary system so safe in renal impairment

36
Q

what are features of Buprenorphine compared to morphine ?

A

Very high affinity to Mop = low Kd, not displaced
long action duration
low Emax as it is partial agonist
Antagonist at Kop

37
Q

what are indications for buprenorphine ?

A

Moderate to sever pain
polypharmacy patients
Opioid addiction

38
Q

what are side effects of Buprenorphine ?

A

Resp depression
Low Bp
Nausea
dizziness

39
Q

what is the absorption of Naloxone ?

A

IV, IM , IN, PO
Low oral bioavail (First pass)
rapid onset of action

40
Q

What is the D, M and E of Naloxone ?

A

D= rapid due to lipophilicity

M and E= renally excreted, within 30-60 Mins

41
Q

what are features of Naxolone ?

A

affinity MOP>DOP>KOP

Greater affinity than morphine , less than Buprenorphine

42
Q

What must you be aware of naxolone in acute setting ?

A

short acting so give long infused dose to avoid secondary OD

43
Q

How does opioid tolerance build ?

A

Up regulation of opioid receptors when using opioids leads to more Mop receptors = increased mount of opioid for cellular response

44
Q

how can stopping an opioid lead to withdrawls ?

A

endogenous opioids cannot initiate a cellular response

45
Q

what is given to opioid addicts during withdrawl and how does it work ?

A

Methadone is given to stop withdrawal effects leading without much of a high . weaning of slowly to allow Mop receptors to down-regulate

46
Q

what patients should you be considerate of when prescribing opioids ?

A 
Manual labourers/Drivers
• Elderly
• Bedbound
• Asthmatics
• Biliary tract obstruction
• Respiratory Diseases
• Renal impairment
• Pregnancy
47
Q

what are contraindications of opioids?

A

Hepatic failure
acute respiratory distress
comatose
Head injuries , raised ICP = M3G causes irritability

48
Q

what should you in do palliative prescribing for opioids ?

A

ignore special considerations
laxatives
if in pain and SOB

Nervous system (20 decks)

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