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CPT > Session 11 Antiemetics And Antidiarrhoeals > Flashcards

Session 11 Antiemetics And Antidiarrhoeals Flashcards

1
Q

What is vomiting?

A

Involuntary, forceful expulsion of gastric contents through the mouth

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2
Q

Describe how vomiting occurs

A

Vomiting centre in medulla —> vomit

  1. Nausea, salivation and sweating
  2. Retrograde peristalsis
  3. Deep inspiration
  4. Closure of glottis
  5. Abdominal muscles contract
  6. Lower oesophageal sphincter relaxes
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3
Q

What makes the vomiting centre ‘go’?

A

Sensory afferents via midbrain

Direct Triggers (needles etc)

Vestibular nuclei

Visceral afferents from gut

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4
Q

What agents (drugs) act on the vestibular nuclei?

A

Muscarinic receptor antagonists

H1 receptor antagonist

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5
Q

What is an example of a muscarinic receptor antagonist?

A

Hyoscine hydrobromide

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6
Q

Muscarinic receptor antagonists MoA?

A

Competitive blockade of muscarinic acetylcholine receptors in the vestibular nuclei and at the CTZone

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7
Q

Good uses of muscarinic receptor antagonists?

A

For people who cant take tablets

Motion sickness

Bowel obstruction

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8
Q

Side effects of muscarinic receptor antagonists?

A

Sedation

Memory problems

Glaucoma

Dry mouth and constipation

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9
Q

How do H1 receptor antagonists work?

A

Centrally

  • acts on the vestibular nuclei
  • inhibits histaminergic signals from the vestibular system to the CTZ in medulla
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10
Q

What are H1 receptor antagonists good for?

A

Motion sickness - long plane journeys

Promethazine = morning sickness in pregnancy

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11
Q

Names of some H1 receptor antagonists?

A 
Cyclizine
Levomepromazine
Cinnirazine
Promethazine
Diphenhydramine
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12
Q

Side effects of H1 receptor antagonists?

A

Sedation

Excitation

Antimuscarinic - dry mouth, constipation, urinary retention

Cardiac toxicity (long QT interval)

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13
Q

What are the two agents that act on visceral afferents in the gut?

A

5HT3 receptor antagonist

D2 receptor antagonists

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14
Q

What cell type produces serotonin? (5-HT)

A

Enterochromaffin cells

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15
Q

What does serotonin do in response to parasympathetic stimulation?

A

Excites enteric neurones

  • smooth muscle contraction increases motility (except in stomach)
  • increases gut secretions
  • regulates appetite
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16
Q

How do 5HT3 receptor antagonists work

A) peripherally
B) centrally

A

Peripherally
* reduced GI motility and reduces GI secretions

Centrally
* acts to inhibit to CTZ

Good for: almost everyone (1st line treatment most of the time)

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17
Q

Examples of names of 5 HT3 receptor antagonists?

A

Ondansetron
Granesitron
Palonosetron

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18
Q

Side effects of 5 HT3 receptor antagonists?

A

Uncommon!

Constipation 
Headache
Elevated liver enzymes
Long QT syndrome 
Extra-pyramidal effects (dystonia, Parkinsonism)
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19
Q

How do the D2 receptor antagonists metoclopramide and domperidone work?

A

Increase ACh at muscarinic receptors in the gut

Promote gastric emptying

  • increase tone at LOS so it closes
  • increase tone and amplitude of gastric contractions
  • decrease tone of pylorus so it opens
  • increase peristalsis
20
Q

What is metoclopramide good for?

A

GORD

Ileus

21
Q

Side effects of metoclopramide?

A

Galactorrhoea via prolactin release

Extra-pyramidal effects - dystonia, Parkinsonism

22
Q

What is domperidone good for?

A

Improving lactation in breastfeeding mothers

23
Q

Side effects of domperidone?

A

Sudden cardiac death (long QT and VT)

Galactorrhoea

24
Q

What agents act on the CTZ?

A

5HT3 receptor antagonists

H1 receptor antagonists

Muscarinic receptor antagonists

D2 receptor antagonists

Corticosteroids

Cannabinoids

NK1 Receptor antagonists

25
Q

Which drugs are good for chemotherapy sickness?

A

D2 receptor antagonists - Haloperidol

Corticosteroids (also perioperative N+V and palliation

Cannabinoids

Neurokinin 1 receptor antagonists

26
Q

How do NK1 receptor antagonists work?

A

Prevent the action of substance P at CTZ and in peripheral nerves

Boosts effects of 5HT3 receptor antagonists

Anxiolytic an antidepressant properties

27
Q

Side effects of NK1 receptor antagonists?

A

Headache
Diarrhoea or constipation
Stevens - Johnson Syndrome

28
Q

Names of some NK1 receptor antagonists?

A

Aprepitant
fosaprepitant
Netupitant

29
Q

Name of a cannabinoid?

30
Q

Side effects of corticosteroids (when treating vomiting) - dexamethasone and methylprednisolone

A

Insomnia
Increased appetite
Increase blood sugar

31
Q

What is first line treatment for motion sickness?

A

Hyoscine hydrobromide

32
Q

What is hyperemeesis Gravidarum?

A

Excessive nausea and vomiting

  • rapid rise in b-HCG stimulates the CTZ
    Typically occurs in weeks 4-16
    Higher risk with multiple pregnancies
  • also dehydration, weight loss, electrolyte imbalance and urinary ketones
33
Q

Treatment of hyperemesis Gravidarum?

A

Promethazine (H1 RAnt) or Prochlorperazine(D2 RAnt)

Then add: metoclopramide (D2 RAnt)

Then add: ondansetron (5HT3 RAnt)

34
Q

What are some risk factors for post-operative nausea and vomiting?

split up into patient, anaesthetic and surgery

A

patient

  • female
  • history of PONV or motion sickness
  • younger age
  • non smoker

anaesthetic

  • general > regional
  • use of volatile gases or NO
  • post op opioids

Surgery

  • duration of operation
  • laparoscopic surgery
35
Q

How does loperamide work in treating diarrhoea?

What type of drug is it?

A

= opioid receptor agonist

decreases tone of longitudinal and circular smooth muscle

reduces peristalsis but increases segmental contractions (more contact with enterocytes for longer)

decreases colonic mass movement by suppressing gastrocolic reflex (stops the urge)

36
Q

Morphine and codeine can also be given to treat diarrhoea. What type of drugs are they and what are some side effects?

A

Opioid receptor agonists

ADR

  • paralytic ileus
  • N+V
  • sedation and addiction
37
Q

What could you recommend for people with chronic diarrhoea (could be IBS, IBD, short bowel, drug side effects etc)

A

To follow the constipating diet

  • white rice - binds stool
  • white bread / pasta - low in fibre

limit fruit to 3 portions per day
avoid caffeine, sorbitol, fatty or spicy foods and fizzy drinks

38
Q

How do osmotic laxatives work? (general)

A

they increase the amount of water in the large bowel

39
Q

How does lactulose work (an osmotic laxative)?

A

draws fluid IN

40
Q

how do macrogols (movicol and cosmocol) work?

  • osmotic laxatives
A

they retain the fluid they came in

movicol is first line - come in sachet form

41
Q

How do stimulant laxatives work?

A

increase intestinal motility

42
Q

What are names of some laxatives?

A 
bisacodyl 
sodium picosulphate 
senna 
co-danthromer 
docusate sodium 
Glycerin suppository
43
Q

Which laxative is a stimulant and a stool softener?

A

docusate sodium

44
Q

Which laxative causes rectal irritation and lubrication?

A

glycerin suppositories

45
Q

What are two names of bulk forming laxatives?

A

ispaghula husk

methylcellulose

46
Q

How do stool softeners work?

A

decrease surface tension of stool

increase penetration of fluid into stool

CPT (23 decks)

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