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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
26
Uses of 5HT3 recpetor antagnists
* Almost everyone- 1st line treatment for almost all vomiting
27
**Mode of action of 5HT3 receptor antagonists**
* Acts as a **visceral afferent in the gut** * **Peripherally** * Reduces GI motility * Reduces GI secretions * **Centrally** * Act to inhibit the CTZ
28
**Adverse drug response 5HT3 receptor antagonists**
* Constipation * Headache * Elevated liver enzymes * Long QT syndrome * Extra pyramidal effects- dystonia, parkinsonism
29
**name some drugs under the class D2 receptor antagonists (only some work on visceral afferents))**
30
uses of D2 receptor antagonists
* **Metoclopramide**- GORD, Ileus * **Domperidone-** improving lactation in breastfeeding mothers
31
MOA of metoclopramide (D2 receptor antagonist)
* 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
32
Domperidone MOA
* Similar mechanisms as metoclopramide * Used to be used very frequently but new evidence and a few high profile cardiac side effects
33
adverse drug response metoclopramide (D2 receptor antaognist)
* Galactorrhoea via prolactin release * Extra-pyramidal effects- dystonia, Parkinson’s
34
adverse drug response domperidone (D2 receptor antaognist)
* Sudden cardiac death (long QT and VT) * Galactorrhoea
35
D2 receptor antagonists which just work on the CTS
36
D2 receptor antagonists which just work on the CTZ- The zines
* Act on the CTZ * May also block H1 and Muscarinic receptors * Good for * Motion sickness * Vertigo * **Prochlorperazine** in pregnancy
37
D2 receptor antagonists which just work on the CTZ- haliperidol uses
* Act on the CTZ * Good for * chemotherapy and palliation
38
D2 receptor antagonists which just work on the CTZ: **Side effects**
* extra-pyramidal effects- dystonia, parkinsonism * sedation * hypotension
39
name some Neurokinin 1 receptor antagonists
40
uses of Neurokinin 1 receptor antagonists
* Chemotherapy (particularly delayed emesis)
41
mode of action of Neurokinin 1 receptor antagonists
* Prevent action of substance P at CTZ and in peripheral nerves * Boosts effect of 5HT3 receptor antagonists * Anxiolytic and antidepressant properties
42
**Adverse drug response** Neurokinin 1 receptor antagonists
* Headache * Diarrhoea/constipation * Steven Johnson syndrome
43
name corticosteroids used as antiemitics
44
**Corticosteroids Uses**
* **Perioperative nausea and vomiting** * **Chemotherapy** * **Palliation**
45
**Mode of action corticosteroids**
* Act on the CTZ * May also have properties of D2 receptor antagonists
46
**Adverse drug response corticosteroids**
* Insomnia * Increased appetite * Increased blood sugar
47
name a cannabinoid
Nabilone (good for sickeness in **chemotherapy**)
48
**Mode of action of cannabinoids**
Act on the CTZ
49
**Adverse drug response cannabinoids**
* Dizziness * Drowsniness
50
which drug for motion sickness whilst driving
* Prevention better than cure * **Hyoscine hydrobromide** = 1st line * however sedating so not good for drive * **Cinnarizines** has fewer side effects
51
which drug for gut problems e.g. infective gastroenteritis vs othe rboewl pathology
* 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
prokinetics
are medications that help control acid reflux e.g. domperidone, metoclopramid, cisapride
53
prokinetics are useful for
GORD Illeus
54
dont use prokinetics if
obstruction or risk of perforation
55
In general if gut problem that is suitable for antiemetic... use this approach
56
examples of direct triggers of the CTZ
* Hormones e.g. hCG in hyperemisis gravidarum * chemotherapy * anaesthetics * opiates
57
hyperemesis gravidarum
* 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
**Treatment of HG**
59
chemotherapy
60
**Anaesthetics**
* Post operative nausea and vomiting * Risk factors:
61
treatment for nausea and vomiting caused by anaesthetics
62
define diarrhea
Having diarrhea means passing loose stools three or more times a day
63
**When to stop diarrhoea?**
* Treat the cause * Increase transit time * Comfort * Prevent incontinence
64
causes of diarrhea
65
**Infective gastroenteritis**
* 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
name some drugs under the class opioid receptor agonist to prvenet diarrhea
loperamide codeine morphine
67
opioid receptor agonists uses
* Diarrhoea * Palliative care
68
loperamide is also known as
imodium
69
MOA of loperamide (imodium)
* 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
codein and morphine work on which receptors
71
**Adverse drug response of opioid receptor agonists**
* Paralytic ileus * Nausea and vomiting * Sedation * Addiction (codeine and morphine)
72
constipating diet used in
* IBS, IBD, short bowel, hypermotility, drug side effect
73
outline constipating diet
* **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
**Constipation treatment**
* 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
medication for constipation
76
types of laxatives
* osmotic * srtimulant * bulk forming * stool softners
77
osmotic laxatives4
* Increase amount of water in the large bowel * Draw water in (lactulose) * Retain the fluid they came with * Macrogols
78
stimulant laxatives
* Increased intestinal motility * Orally or per rectum * Docusate sodium acts as stimulant and stool softener * Glycerin suppositories cause rectal irritation and lubrication
79
**Bulk forming laxation**
* Medicinal fibre * Soften stool * Can also be used for diarrhoea
80
**Stool softeners e.g. via enema**
* Decrease surface tension of stool * Increase penetration of fluid into stool

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

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