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Clinical Pharmacology, Therapeutics & Intro to Prescribing > Lecture 20- Antiemetics > Flashcards

Lecture 20- Antiemetics Flashcards

1
Q

What is vomiting

A

Involuntary, forceful expulsion of gastric contents through the mouth

  • Protective mechanism to remove toxins or to teach you to avoid unpleasant situations
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2
Q

Vomiting is different to regurgitation​

A
  • more of a mechanical problem where food and liquid hasn’t got to the stomach and is brought up effortlessly
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3
Q

what is actually going on with vomiting

A

Vomiting centre in medulla signals to vomit..

  1. nausea, salivation, sweating
  2. retrograde peristalsis
  3. deep inspiration
  4. closure of glottis
  5. abdominal muscles contract
  6. lower oesophageal sphincter relaxes
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4
Q

what makes the vomiting centre in the medulla go

A

when the chemoreceptor trigger zone (CTZ) is stimulated

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5
Q

what triggers the chemoreceptor trigger zone (CTZ)

A
  • Sensory afferents via the midbrain
  • Vestibular nuclei
  • Visceral afferents from gut
  • Direct triggers e.g. drugs, anaesthetics, hormones
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6
Q

the chemoreceptor trigger zone (CTZ)found in

A

the floor of the fourth ventricles on the blood side of the bbbà not as thick here therefore some substances can come across

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7
Q

How can we make vomiting stop?

A
  • Just removed the triggers?
    • Remove sensory disgust
    • Don’t go on a long journey
    • Don’t take drugs
  • However not always practical so we use drugs
    • Can use drugs to target different points of the system
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8
Q

Drugs used to reduce stimulation of the chemoreceptor trigger zone (CTZ)

A

Agents acting on the vestibular nuclei

Agents acting on visceral afferents in the gut

Agents acting on the CTZ

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9
Q

Agents acting on the vestibular nuclei

A
  • Muscarinic receptor Antagonists
  • H1 receptor antagonists
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10
Q

Agents acting on visceral afferents in the gut

A
  • 5HT3 receptor Antagonists
  • D2 receptor antagonists
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11
Q

Agents acting on the CTZ

A
  • 5HT3 receptor antagonists
  • H1 receptor antagonists
  • Muscarinic receptor antagonists - D2 receptor antagonists
  • Corticosteroids
  • Cannabinoids
  • NK1 receptor antagonists
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12
Q

drugs under the class muscarinic receptor antagonists

A

hyoscine hydrobromide

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13
Q

uses of hyoscine hydrobromide (a muscarinic receptor antagonist)

A
  • Good for people who cant take tables (patch)
  • Motion sickness
  • Bowel obstruction
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14
Q

Mode of action of hyoscine hydrobromide (muscarinic receptor antagonist)

A
  • Competitive blockade of muscarinic acetylcholine receptors
    • In the vestibular nuclei
    • Also at the CTZ
  • Remember these receptor are all over the body- part of the parasympathetic nervous system body – part of the parasympathetic nervous system!!
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15
Q

Adverse drug response of hyoscine hydrobromie think anti-muscarinic effects

A
  • Sedation
  • Memory problems
  • Glaucoma
  • Dry mouth and constipation. (can be used for people who oversecrete saliva)
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16
Q

contraindications of hyoscine hydrobromide

A
  • Cardiac issues
  • diarrhoea
  • elderly
  • gastro-oesophageal reflux disease
  • hypertension
  • hyperthyroidism (due to association with tachycardia);
  • individuals susceptible to angle-closure glaucoma;
  • prostatic hyperplasia (in adults)
  • pyrexia
  • ulcerative colitis
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17
Q

name some H1 receptor antagonists

A
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18
Q

uses of H1 receptor antaognists e.g. cyckizine

A
  • Motion sickness- long plane journeys
  • Promethazine- morning sick ness in pregnancy
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19
Q

Mode of action of H1 receptor antagonists e.g. cyclizine, promethazine

A
  • Acts on the vestibular nuclei
  • Inhibits histaminergic signals from the vestibular system to the CTZ in medulla
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20
Q
A
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21
Q

Adverse drug response of H1 receptor antagonists e.g. cyclizine, promethazine

A
  • Sedation
  • Excitation
  • Antimuscarinic
    • Dry mouth
    • Constipation
    • Urinary retention
  • Cardiac toxicity (long OT interval)
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22
Q

contraindication of H1 recpetor antagonists

A

Contraindication

  • Cyclizine- little old ladies and children (disorientation)
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23
Q

serotonin (5HT) in the gut

A
  • 95% serotonin in the body is located in the gut
  • Produced by the enterochromaffin cells
  • In response to parasympathetic stimulation, serotonin excites enteric neurones
    • Smooth muscle contraction increases motility (except in the stomach)
    • Increases gut secretions
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24
Q

name some drugs under the 5HT3 recepor antagonists

A
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25
Q
A
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26
Q

Uses of 5HT3 recpetor antagnists

A
  • Almost everyone- 1st line treatment for almost all vomiting
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27
Q

Mode of action of 5HT3 receptor antagonists

A
  • Acts as a visceral afferent in the gut
  • Peripherally
    • Reduces GI motility
    • Reduces GI secretions
  • Centrally
    • Act to inhibit the CTZ
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28
Q

Adverse drug response 5HT3 receptor antagonists

A
  • Constipation
  • Headache
  • Elevated liver enzymes
  • Long QT syndrome
  • Extra pyramidal effects- dystonia, parkinsonism
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29
Q

name some drugs under the class D2 receptor antagonists (only some work on visceral afferents))

A
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30
Q

uses of D2 receptor antagonists

A
  • Metoclopramide- GORD, Ileus
  • Domperidone- improving lactation in breastfeeding mothers
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31
Q

MOA of metoclopramide (D2 receptor antagonist)

A
  • increases Ach at muscarinic receptors in the gut
    • Promoting gastric emptying
      • Increase tone at lower oesophageal sphincter so it closes
      • Increases tone and amplitude of gastric contractions
      • Decreases tone of pylorus so its open
    • Increases peristalsis
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32
Q

Domperidone MOA

A
  • Similar mechanisms as metoclopramide
  • Used to be used very frequently but new evidence and a few high profile cardiac side effects
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33
Q

adverse drug response metoclopramide (D2 receptor antaognist)

A
  • Galactorrhoea via prolactin release
  • Extra-pyramidal effects- dystonia, Parkinson’s
34
Q

adverse drug response domperidone (D2 receptor antaognist)

A
  • Sudden cardiac death (long QT and VT)
  • Galactorrhoea
35
Q

D2 receptor antagonists which just work on the CTS

36
Q

D2 receptor antagonists which just work on the CTZ- The zines

A
  • Act on the CTZ
  • May also block H1 and Muscarinic receptors
  • Good for
    • Motion sickness
    • Vertigo
    • Prochlorperazine in pregnancy
37
Q

D2 receptor antagonists which just work on the CTZ- haliperidol uses

A
  • Act on the CTZ
  • Good for
    • chemotherapy and palliation
38
Q

D2 receptor antagonists which just work on the CTZ: Side effects

A
  • extra-pyramidal effects- dystonia, parkinsonism
  • sedation
  • hypotension
39
Q

name some Neurokinin 1 receptor antagonists

40
Q

uses of Neurokinin 1 receptor antagonists

A
  • Chemotherapy (particularly delayed emesis)
41
Q

mode of action of Neurokinin 1 receptor antagonists

A
  • Prevent action of substance P at CTZ and in peripheral nerves
  • Boosts effect of 5HT3 receptor antagonists
  • Anxiolytic and antidepressant properties
42
Q

Adverse drug response Neurokinin 1 receptor antagonists

A
  • Headache
  • Diarrhoea/constipation
  • Steven Johnson syndrome
43
Q

name corticosteroids used as antiemitics

44
Q

Corticosteroids Uses

A
  • Perioperative nausea and vomiting
  • Chemotherapy
  • Palliation
45
Q

Mode of action corticosteroids

A
  • Act on the CTZ
  • May also have properties of D2 receptor antagonists
46
Q

Adverse drug response corticosteroids

A
  • Insomnia
  • Increased appetite
  • Increased blood sugar
47
Q

name a cannabinoid

A

Nabilone (good for sickeness in chemotherapy)

48
Q

Mode of action of cannabinoids

A

Act on the CTZ

49
Q

Adverse drug response cannabinoids

A
  • Dizziness
  • Drowsniness
50
Q

which drug for motion sickness whilst driving

A
  • Prevention better than cure
  • Hyoscine hydrobromide = 1st line
    • however sedating so not good for drive
  • Cinnarizines has fewer side effects
51
Q

which drug for gut problems e.g. infective gastroenteritis vs othe rboewl pathology

A
  • Infective Gastroenteritis- defence mechanisms that you need – don’t need antiemetic
  • Other bowel pathology which causes vomiting
    • Gastric cancer
    • UC
    • GORD
    • Appendicitis
  • Don’t want to give drugs straight away e.g. consider a nasogastric tube à removing content without pt having to vomit
  • Prokinetics (control acid reflux)
52
Q

prokinetics

A

are medications that help control acid reflux e.g. domperidone, metoclopramid, cisapride

53
Q

prokinetics are useful for

A

GORD

Illeus

54
Q

dont use prokinetics if

A

obstruction or risk of perforation

55
Q

In general if gut problem that is suitable for antiemetic… use this approach

56
Q

examples of direct triggers of the CTZ

A
  • Hormones e.g. hCG in hyperemisis gravidarum
  • chemotherapy
  • anaesthetics
  • opiates
57
Q

hyperemesis gravidarum

A
  • Rapid rise in Beta- HCG stimulates the CTZ
  • Typically week 4-16 but may continue beyond
  • Higher risk with multiple pregnancies
  • more than just morning sickness
    • dehydration
    • 5% weight loss
    • Electrolyte imbalance

Urinary ketones

58
Q

Treatment of HG

59
Q

chemotherapy

60
Q

Anaesthetics

A
  • Post operative nausea and vomiting
  • Risk factors:
61
Q

treatment for nausea and vomiting caused by anaesthetics

62
Q

define diarrhea

A

Having diarrhea means passing loose stools three or more times a day

63
Q

When to stop diarrhoea?

A
  • Treat the cause
  • Increase transit time
  • Comfort
  • Prevent incontinence
64
Q

causes of diarrhea

65
Q

Infective gastroenteritis

A
  • Viral, bacterial or protozoal
  • May be toxin mediated
  • Osmotic or secretory
  • Treatment
    • Don’t want to stop diarrhoea–> getting rid of toxins
    • May give dioralyte to stop dehydration
66
Q

name some drugs under the class opioid receptor agonist to prvenet diarrhea

A

loperamide

codeine

morphine

67
Q

opioid receptor agonists uses

A
  • Diarrhoea
  • Palliative care
68
Q

loperamide is also known as

69
Q

MOA of loperamide (imodium)

A
  • Exogenous opioid
  • Specific to U receptor in the myenteric plexus
  • Decreases tone of longitudinal and circular smooth muscles
  • Reduces peristalsis but increases segmental contraction
  • Decreases colonic mass movement by suppressing gastrocolic
70
Q

codein and morphine work on which receptors

71
Q

Adverse drug response of opioid receptor agonists

A
  • Paralytic ileus
  • Nausea and vomiting
  • Sedation
  • Addiction (codeine and morphine)
72
Q

constipating diet used in

A
  • IBS, IBD, short bowel, hypermotility, drug side effect
73
Q

outline constipating diet

A
  • What to eat:
    • Bananas
    • White rice
    • White bread/pasta
    • High in potassium and fibre
    • Binds stool
    • Low in fibre
  • Limit
    • Fruit to 3 portions
    • Caffeine
    • Sorbitol
    • Fatty or spicy foods
    • Fizzy drinks
  • Consider probiotics to re-instate a balanced intestinal flora
74
Q

Constipation treatment

A
  • 14% prevalence of chronic idiopathic constipation
  • Diet and lifestyle changes
    • Drink more water
    • Increase fibre intake
      • Wholegrain foods, fruit and veg, nuts, pulses
    • Regular exercise
    • Toilet routine and positioning
75
Q

medication for constipation

76
Q

types of laxatives

A
  • osmotic
  • srtimulant
  • bulk forming
  • stool softners
77
Q

osmotic laxatives4

A
  • Increase amount of water in the large bowel
    • Draw water in (lactulose)
  • Retain the fluid they came with
    • Macrogols
78
Q

stimulant laxatives

A
  • Increased intestinal motility
  • Orally or per rectum
  • Docusate sodium acts as stimulant and stool softener
  • Glycerin suppositories cause rectal irritation and lubrication
79
Q

Bulk forming laxation

A
  • Medicinal fibre
  • Soften stool
  • Can also be used for diarrhoea
80
Q

Stool softeners e.g. via enema

A
  • Decrease surface tension of stool
  • Increase penetration of fluid into stool

Clinical Pharmacology, Therapeutics & Intro to Prescribing (39 decks)

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