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Pharm OTL > GI - Antiemetics > Flashcards

GI - Antiemetics Flashcards

1
Q

Where is the chemoreceptor trigger zone?

A

Bottom of the fourth ventricle in the medulla

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2
Q

State four inputs to the CTZ

A
  • Sensory afferents via the midbrain (see, smell, taste something gross.
  • Vestibular nuclei (motion sickness)
  • Visceral afferents from the gut (stretched, inflamed)
  • Direct triggers (drugs, toxins)
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3
Q

List two drug classes that act on the vestibular nuclei

A

Muscarinic receptor antagonists

H1 receptor antagonists

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4
Q

List two drug classes that act on the visceral afferents from the gut

A

5HT3 antagonists

D2 receptor antagonists

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5
Q

List seven dug classes that act directly on the CTZ

A 
D2 receptor antagonists
5HT3 receptor antagonists
Muscarinic receptor antagonists
H1 receptor antagonists
Corticosteroids
Cannabinoids
NK1 receptor antagonists
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6
Q

Name a muscarinic receptor antagonist

A

Hyoscine hydrobromide (hyoscine - high sea .·. motion sickness)

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7
Q

What is the MoA of muscarinic receptor antagonists?

A

Competitive blocking of ACh receptors in the Psymp NS in the vestibular nuclei and CTZ

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8
Q

State two uses of muscarinic receptor antagonists

A
  • People who can’t take tablets (available as a patch)
  • Motion sickness
  • Bowel obstruction
  • Palliative care
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9
Q

State two side effects of muscarinic receptor antagonists

A 
Sedation
Memory problems
Glaucoma
Dry mouth
Constipation
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10
Q

State two examples of H1 receptor antagonists

A

Cyclizine
Levomepromazine
Promethazine

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11
Q

What is the MoA of H1 receptor antagonists?

A

Inhibit histaminergic signals from the vestibular system to the CTZ

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12
Q

State two uses for H1 receptor antagonists

A

Motion sickness for long journeys when you want to sleep

(Promethazine) morning sickness in pregnancy

GI pathology e.g. Crohn’s, appendicitis, UC

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13
Q

Why shouldn’t cyclizine be used for little old ladies and children?

A

Sedation or excitation effects

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14
Q

State two side effects of H1 receptor antagonists

A

Sedation or excitation
Dry mouth
Constipation
Long QT interval

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15
Q

Name a 5HT3 receptor antagonists

A

Ondansetron

Granesitron

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16
Q

What is the MoA of 5HT3 receptor antagonists?

A

Antagonising serotinin produced by enterochromaffin cells leads to:

  • Reduces smooth muscle cell contraction
  • Decreases gut secretions

Also inhibs the CTZ

17
Q

What are 5HT3 receptor antagonists used for?

A

Almost everyone - 1st line most of the time

Chemo when medium risk

Second line in hyperemesis gravidarum

GI pathology

18
Q

State two side effects of 5HT3 receptor antagonists

A 
Constipation
Headache
Long QT syndrome
Elevated liver enzymes
Parkinsonism
19
Q

Name two D2 receptor antagonists that act on the visceral afferents in the gut and the CTZ

A

Metacloperamide

Domperidone

20
Q

Name two other D2 receptor antagonists that only act on the CTZ

A

Chlorpromazine
Haloperidol
Levomepromazine
Prochlorperazine

(Cross over with H1 receptor antagonists - stuff can do two things)

21
Q

What is a MoA of D2 receptor antagonists?

A

Acts on the CTZ

Acts as a muscarinic and 5HT3 antagonist

Promotes gastric emptying

  • Increased tone at the LOS
  • Increased tone and amplitude of gastric contractions
  • Decreased tone at the pylorus

Inreased peristalsis in the gut

22
Q

State two uses of the D2 receptor antagonists that act on the visceral afferents in the gut

A

GORD

Ileus

Second line in hyperemesis gravidarum

Rescue medication in chemo

23
Q

State two uses of D2 receptor antagonists that act on the CTZ

A

Motion sickness
Vertigo
Prochlorperazine first line in pregnancy
Haloperidol for chemo and palliation

24
Q

State two side effects of D2 receptor antagonists

A

Galactorrhoea
Parkinsonism
Sedation
Hypotension

25
Q

Name two corticosteroids

A

Dexamethasone
Methylprednisalone
Betamethasone

26
Q

What is the MoA of corticosteroids as an antiemetic?

A

Acts on the CTZ

27
Q

State two uses for corticosteroids

A

Preoperative nausea and vomiting
Low risk chemotherapy
Palliation

28
Q

State two side effects of coricosteroids

A

Insomnia
Increased blood sugar
Increased appetite

29
Q

Name a cannabinoid

A

Nabilone

30
Q

When are cannabinoids used?

A

Last line in chemo

31
Q

State a side effect of cannabinoids

A

Dizziness

Drowsiness

32
Q

Name a neurokinin 1 receptor antagonist

A

Aprepitant

Fosaprepitant

33
Q

What is the MoA of neurokinin 1 receptor antagonists?

A

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

Boosts effects of the 5HT3 receptor antagonists when given together

34
Q

What are neurokinin 1 receptor antagonists used for?

A

High risk chemo-induced emesis

35
Q

State a side effect of neurokinin 1 receptor antagonists

A

Headache
Diarrhoea
Constipation
Stevens-Johnson syndrome

36
Q

What would you use for hyperemesis gravidarum?

A

Promethazine or prochlorperazine
Add metacloperamide
Add ondansetron

37
Q

What would you use for chemo-induced emesis?

A

Dexamethasone
Add ondansetron
Add aprepitant

Use metaclopramide for rescue

Pharm OTL (18 decks)

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