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CPT > L17 - Antiemetics > Flashcards

L17 - Antiemetics Flashcards

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1
Q

Vomiting

A

Involuntary forceful expulsion of gastric contents through the mouth

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2
Q

Regurgitation

A

Passive overflow of gastric or oesophageal contents

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3
Q

Mechanism of vomiting

A
  1. Stimulus stimulates the vomiting centre in the medulla (chemoreceptor trigger zone)
  2. Nausea is felt with increased salivation and sweating
  3. Retrograde peristalsis of small bowel also causes nausea
  4. Deep inspiration
  5. Closure of glottis - prevents aspiration
  6. Abdominal muscles contract
  7. Lower oesophageal sphincter relaxes
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4
Q

What stimulates the chemoreceptor trigger zone in the medullar?

A
  1. Sensory afferents via the midbrain
    - squeamish
  2. Vestibular nuclei
    - inner ear infections
    - motion sickness
    - sea sickness
    - vertigo
  3. Visceral afferent form the gut
    - problem with gut transmits via vagus nerve
  4. Direct triggers
    - drugs - chemotherapy, anaesthetics, opiates
    - hormones - B- HCG
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5
Q

Chemoreceptor trigger zone

A
  • In blood side of the blood brain barrier

- located on the floor of the fourth ventricle within the area postrema

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6
Q

Drugs acting on the vestibular nuclei

A
  • muscarinic receptor antagonists

- H1 receptor antagonists

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7
Q

Drugs acting on the visceral afferent from the gut

A

Serotonin antagonists

D2 receptor antagonists

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8
Q

Drugs that act directly on the CTZ

A 
D2 receptor antagonists 
Serotonin receptor antagonist 
Muscarinic receptor antagonis5 
H1 receptor antagonist 
Corticosteroids
Cannabinoids 
NK1 receptor antagonist
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9
Q

Muscarinic receptor antagonist example

A

Hyoscine hydrobromide

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10
Q

Muscarinic receptor antagonist mechanism of action

A

Competitive blockade of muscarinic acetylcholine receptors

  • in the vestibular nuclei
  • in the CTZ
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11
Q

When are muscarinic receptor antagonists used

A

People who can’t take tablets - patch
Motion sickness
Bowel obstruction - reduce parasympathetic activity in the gut

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12
Q

Side effects of hyoscine hydrobromide

A 
Sedation 
Memory problems
Glaucoma 
Dry mouth 
Constipation
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13
Q

H1 recepteor antagonists

A 
Cyclizine 
Levomepromazine 
Cinnirazine 
Promethazine 
Diphenhydramine
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14
Q

H1 receptor antagonist mechanism of action

A

Acts on:

- vestibular nuclei x inhibits the histaminergic signals from the vestibular system to the CTZ in the medulla

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15
Q

When is H1 receptor antagonists used

A

Motion sickness - long plane journeys

Promethazine - morning sickness in pregnancy

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16
Q

What is cyclizine bad for

A

For little old ladies and children
Causes excitation and wacky-ness
Driving

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17
Q

Side effects of H1 receptor antagonists

A

Sedation
Excitation
Anti- muscarinic - dry mouth, constipation and urinary retention
Cardiac toxicity - long QT

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18
Q

Serotonin action in the gut

A

95% of serotonin is in the gut - produced by enterochromaffin cells due to parasympathetic stimulation

Serotonin excites enteric neurones for:

  • smooth muscles contraction - increases motility except stomach
  • increases gut secretions
  • regulates appetite
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19
Q

Serotonin receptor antagonist examples

A

Ondansetron - most common
Granesitron
Palonosetron

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20
Q

Mechanisms of action of serotonin receptor anatagonists

A

Centrally:
- inhibits the CTZ

Peripherally:

  • reduces gut motility - prevents retrograde peristalsis
  • reduces gut secretions - decreases volume of the vomit

Use:
- good for almost everyone - 1st line

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21
Q

Side effects of serotonin receptor antagonists

A 
Constipation 
Headache 
Elevated liver enzymes 
Long QT syndrome 
Extra-pyramidal effects - dystonia and Parkinsonism
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22
Q

D2 receptor antagonist examples

A

Metoclopramide
Domperidone

Prochlorperazine
Levomepromazine
Chlorpromazine
Haloperidol

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23
Q

Mechanism of action of metoclopramide and domperidone

A
  • Increases acetylcholine at muscarinic receptors in the gut
  • increases parasympathetic activity
  • increases gastric emptying
  • increases tone of the lower oesophageal sphincter (closes)
  • increases tone and amplitude of gastric contractions - pushing food downs
  • decreases tone of the pylorus sphincter - opens allowing gastric emptying
  • increases peristalsis
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24
Q

When is metoclopramide used?

A

GORD

Ileus

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25
Q

Ileus

A

Loss of muscle contraction therefore loss of peristalsis

Occurs post surgery or after a significant infection

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26
Q

Side effects of metoclopramide

A

Galactorrhoea - prolactin release

Extra pyramidal effects - dystonia, Parkinsonism

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27
Q

Domperidone use

A

Improving lactation in breastfeeding mothers as side effects is galactorrhoea

  • increased risk of sudden cardiac death - long QT and VT
  • not used commonly
28
Q

Mechanism of action of the ‘zine’ D2 receptor antagonists

A

Act on the CTZ

Block H1 and muscarinic receptors as well

29
Q

When are the zine D2 receptor anatagonists used

A

Motion sickness

Vertigo

30
Q

When is prochlorperazine used

A

During pregnancy

31
Q

When is Haloperidol used

A

Chemotherapy and palliation

32
Q

Side effects of other D2 receptor anatagonists

A

Sedation
Hypotension
Extra pyramidal effects - dystonia and Parkinsonism

33
Q

Corticosteroid examples

A

Dexamethasone

Methylprednisolone

34
Q

Mechanism of action of corticosteroids and use

A

-assumed to act on CTZ and D2 receptors

Use:

  • chemotherapy
  • palliation - appetite loss
  • perioperative nausea and vomiting
35
Q

Side effects of corticosteroids

A

Insomnia
Increased appetite
Increased blood sugar

  • long term use can cause Cushing’s syndrome but corticosteroids are normally used short term
36
Q

Cannabinoid example

A

Nabilone

37
Q

Nabilone mechanism, use and side effects

A

Mechanism: assumed to act on CTZ

Use: last line for chemotherapy nausea and vomiting

Side effects: dizzying and drowsiness

38
Q

Neurokinin 1 receptor anatagonists examples

A

Aprepitant
Fosaprepitant
Netupitant

39
Q

Mechanism of nuerokinin -1 receptor antagonists

A
  • Prevents the action of substance P at CTZ and in peripheral nerves - pain killer
  • Boosts effects of serotonin receptor antagonists
  • anxiolytics and antidepressant properties
40
Q

When are neurokinin-1 receptor antagonists used

A

In delayed emesis with chemotherapy

41
Q

Side effects of neurokinin-1 receptor antagonists

A

Headache
Constipation or diarrhoea
Steven Johnson syndrome

42
Q

Motion sickness treatment

A

Give drug before trigger

1st line for plane journeys:
- hyoscine hydrobromide - muscarinic receptor anatagonist (sedating)

1st line for driving:
Cinnirazine - H1 receptor antagonist (fewer side effects)

43
Q

Nasogastric tube

A

Mechanically decompress the stomach

Lets fluid out without vomiting

44
Q

Prokinetics

A

Increases gut motility

Examples:

  • domperidone
  • metoclopramide

Used in:

  • GORD
  • Ileus

Not used in:

  • obstruction
  • risk of perforation
45
Q

Drugs for nausea

A

1st line - ondansetron - serotonin receptor antagonist

AND/OR
cyclizine- H1 receptor antagonists

THEN
Dexamethasone- corticosteroid

Dexamethasone -

46
Q

Hyperemesis gravidarum

A

Rapid rise in B-HCG stimulates the CTZ
Typically in weeks 4-16
Higher risk with multiple pregnancies

Causes:

  • more than morning sickness
  • dehydration
  • 5% weight loss
  • electrolyte imbalance
  • urinary ketones
47
Q

Drugs for hyperemesis gravidarum

A

Promethazine - H1 receptor antagonist
OR
Prochlorperazine - D2 receptor antagonist

THEN ADD
Metoclopramide- D2 receptor antagonist and prokinetic

THEN ADD
Ondansetron - serotonin receptor antagonist

48
Q

Ondansetron risk on pregnant ladies

A

If given in the 1st trimester, there is greater risk of cleft lip therefore last line

49
Q

Drugs to treat chemotherapy risk of emesis

A

Low risk:

  • dexamethasone
  • rescue: metoclopramide

Moderate risk:

  • dexamethasone
  • and ondansetron
  • rescue: metoclopramide

High risk:

  • dexamethasone
  • and ondansetron
  • and aprepitant
  • rescue: metoclopramide
50
Q

Post operative nausea and vomiting risk factors

A 
Female 
History of post operative N+V
Young 
Non smoker
General anaesthetic + use of nitrous oxide 
Post operative opioids 
Duration of surgery 
Laparoscopy
51
Q

Infective gastroenteritis

A

Viral, bacterial or protozoan

  • can be osmotic or secretory
  • May be toxin mediated
52
Q

How to treat diarrhoea

A
  • treat the cause e.g. Crohn’s disease
  • increase transit time
  • increase comfort - minimise sore bottom
  • prevent incontinence
53
Q

Medication to treat diarrhoea

A

Opioid receptor antagonists:

  • loperamide
  • codeine
  • morphine
54
Q

Loperamide

A

1st line
Specific to MOP in the myenteric plexus of the gut (less side effects)

  • decreases tone of the longitudinal and circular smooth muscle
  • reduces peristalsis
  • increases segmental contractions (shuttling) - gut contents are in contact with enterocytes for longer
  • decreases colonic mass movement by suppressing the gastrocolic reflex
55
Q

Side effects of opioid receptor antagonists

A
  • paralytic ileus
  • nausea and vomiting
  • sedation
  • addiction (codeine and morphine)
56
Q

Constipating diet

A

For long term loose stools - IBD, IBS, Short bowel, hyper mobility or dug side effect

  • bananas
  • white rice, bread or pasta
  • limit fruit to 3 per day
  • avoid caffeine, sorbitol, fatty or spicy foods and fizzy drinks
  • probiotics
  • low in fibre and high in potassium
  • binds to stool
57
Q

Diet and life style changes to help constipation

A
  • drink more water
  • increase fibre intake - fruit, pulses, nuts and veg + whole grains
  • regular exercise
  • toilet routine and positioning
58
Q

Education for constipation

A

Laxatives:

  • osmotic - mush
  • stimulants - push
  • bulk forming
  • stool softener

Enemas

  • osmotic
  • stimulant
59
Q

Osmotic laxatives

A

Increase the amount of water in the large bowel

  • draw fluid in: lactulose
  • retain the fluid they came in with - macrogols
60
Q

Macrogols

A

Movicol
Cosmocol

  • take with squash, yoghurt and ice cream
  • safe an can take up to 12 sachets per day
61
Q

Stimulant laxatives

A
  • Increases the intestinal motility

- oral or per rectum

62
Q

Stimulant laxative examples

A 
Bisacodyl
Sodium picosulphate 
Senna 
Co-danthromer 
Docusate sodium 
Glycerin
63
Q

Docusate sodium

A

Stimulant and stool softener

64
Q

Glycerin

A

Suppository

Causes rectal irritation and lubrication

65
Q

Bulk forming laxative examples and mechanism

A

Ispagula husk
Methylcellulose

Acts as medicinal fibre to bulk stool - feel solid stool which triggers the gastrocolic reflex
- can be used in constipation and diarrhoea

66
Q

Stool softener

A

Mainly enemas
Decreases surface tension of stool
Increase penetration of fluid into stool

  • docusate sodium
  • glycerin suppository
  • arachis oil
  • liquid paraffin

CPT (23 decks)

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