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Semester 4 - Clinical Pharmacology And Therapeutics > Antiemetics And Antidiarrhoeals > Flashcards

Antiemetics And Antidiarrhoeals Flashcards

1
Q

What drugs at on the vestibular nuclei?

A

Muscarinic Receptor Antagonists

H1 receptor antagonists

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2
Q

What is the main Muscarinic receptor antagonist?

A

Hyosine hycobromide

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3
Q

How does hyosine hycobromide work?

A

Competitive blockade of Muscarinic ACh receptors in the vestibular nuclei and the CTZ.

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4
Q

Who is hyosine good for?

A

People who cant take tablets (patch)
Motion sickness
Bowel obstruction

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5
Q

What are the side effects of hyosine?

A

Dry mouth and constipation
Sedation
Memory problems
Glaucoma

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6
Q

What are the main H1 receptor antagonists?

A 
Cyclizine (not children or old ladies as sedation and excitation are more prominent) 
Levomepromazine
Cinnirazine
Promethazine
Diphenhydramine
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7
Q

How do H1 receptor antagonists work?

A

Centrally:
Vestibular nuclei
Inhibits histaminergic signals from the vestibular system to the CTZ in medulla

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8
Q

Why are H1 good for / not good for?

A

Good:
Motion sickness - long place journeys
Promethazine - morning sickness in pregnancy

Not good:
Cyclizine -little old ladies and children

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9
Q

What are the side effects of H1?

A

Sedation
Excitation
Antimuscarinic - dry mouth, constipation, urinary retention
Cardiac toxicity (long QT)

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10
Q

What agents act on visceral afferents?

A

5HT3 receptor antagonists

D2 receptor antagonists

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11
Q

How does serotonin normally work?

A

95% of serotonin in the body is located int he gut and produced by enterochromaffin cells.

In response to parasympathetic stimulation, serotonin excited exterior neurones:
Smooth muscle contraction increases motility (except in stomach)
Increases gut secretions.

It also regulates appetite.

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12
Q

What are the main 5HT3 receptor antagonists?

A

Ondansetron
Granesitron
Palonosetron

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13
Q

How do 5HT3 receptor antagonists work?

A

They work peripherally to reduce GI motility and secretions.

They work centrally to inhibit the CTZ.

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14
Q

Side effects of 5HT3 receptor antagonists?

A 
Constipation
Headache
Elevated liver enzymes
Long QT syndrome
Extra-pyramidal effects - dystonia, parkinsonism
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15
Q

Main D2 receptor antagonists?

A

Metaclopramide

Domperidone

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16
Q

How does metaclipramide work?

A

Increases acetylcholine at muscarinic receptors in the gut.

Promotes gastric emptying - Increases tone at LOS so it closes, Increases time and amplitude of gastric contractions, Decreases tone of pylorus so it opens.

Increases peristalsis

Good for:
GORD
Ileus

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17
Q

What are the side effects of metaclopromide?

A

Galactorrhoea via prolactin release

Extra-pyramidal effects - dystonia, Parkinsonism

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18
Q

How does domperidone work?

A

Similar to metoclopramide - increases ACh at mAChR in gut.
Promote gastric emptying
Increase peristalsis

Used to be popular but increased risk of significant cardiac effects.

Good for improving lactation in breastfeeding mothers

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19
Q

What are the side effects of Domperidone?

A

Sudden cardiac death - long QT and VT (because of this, now used less)

Galactorrhoea

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20
Q

How does Haloperidol work and who is it good for?

A

Act on CTZ
Good for chemo and palliative.

This is also an antipsychotic.

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21
Q

Steroid examples?

A

Dexamethasone

Methylprednisolone

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22
Q

How do steroids work as antiemmetics?

A

Assumed to act on CTZ.

May also have properties of D2 receptor antagonists.

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23
Q

Who are corticosteroids used for?

A

Peri-operative nausea and vomiting
Chemotherapy
Palliation

24
Q

Side effects of steroids?

A

Insomnia
Increased appetite
Increased blood sugar

25
Q

Cannabinoids example

A

Nabolone

26
Q

How do cannabinoids work and what are the side effects?

A

Act on CTZ (assumed)
Good for chemotherapy

Side effects:
Dizziness
Drowsiness

27
Q

Give examples of neurokinin 1 receptor antagonists

A

Aprepitant
Fosaprepitant
Netupitant

28
Q

How do Neurokinin 1 receptor antagonists work?

A

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

Boosts effects of 5HT3 receptor antagonist.

Anxiolytic and antidepressant properties

29
Q

Side effects of Neurokinin 1 receptor antagonists?

A

Headache
Diarrhoea / Constipation
Stevens-Johnson syndrome

30
Q

Different between motion sickness drugs?

A

Hyosine - 1st line but drowsy

Cinnirazine - less drowsy

31
Q

What are prokinetics?

A 
Domperidone 
Metaclopramide (Cisapride)
32
Q

When are prokinetcs useful?

A

GORD

Ileus

33
Q

When dont you use prokinetics?

A

Obstruction

Risk of perforation

34
Q

How do you treat sickness?

A

Ondansetron (5HT receptor antagonist)
snd/or
Cyclizine (H1 receptor antagonist)

Then add:
Dexamethasone (corticosteroid)

35
Q

What can directly trigger CTZ?

A

Hormones - hyperemesis gravidarum

Drugs
Chemotherapy
Anaesthetics
Opiates
Many others!
36
Q

What is hyperemesis Gravidarum?

A

Rapid rise in beta hCG stimulates CTZ.
Typically weeks 4-16 but may continue beyond
Higher risk with multiple pregnancies

More than just ‘morning sickness’ - dehydration, 5% weight loss, electrolyte imbalance, urinary ketones

37
Q

What are the best drugs for hyperemesis Gravidarum?

A

Promethazine (H1 receptor antagonist) or Prochlorperazine (D2 receptor antagonist)

Then add:
Metaclopramide (D2 receptor antagonist)

Then add:
Ondansetron (5HT3 receptor antagonist)

38
Q

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

A

Female
Phobia
Young age
Non Smoker

General> Regional anaesthetic
Volatile anaesthetics
Post-operative opioids

Duration of operation
Laparoscopic Surgery

39
Q

What is the most common class of drugs used to treat diarrhoea?

A

Opioid receptor agonist

40
Q

Give examples of opioid receptor agonist

A

Loperamide (most common)

41
Q

How does loperamide work?

A

It is specific to the u (MOR / mu) receptors in the myenteric plexus

Decreases tone of longitudinal circular smooth muscle
Reduces peristalsis but increases segmental contractions

Decreases colonic mass movements by suppressing gastrocolic reflex.

42
Q

How do opioid receptor agonist (morphone / codine ) work?

A

Act on u and d receptors

Similar to loperamide.

More often used for patients that also have pain.

43
Q

SIde effects of opioid receptor agonist?

A

Paralytic Ileus
Nausea and Vomiting
Sedation and Addiction (codeine and morphine)

44
Q

What effect does fibre have on your stools?

A

Lots - loose stools

Not much - constipated

45
Q

What is the diet for people with long term loose stools?

A

(IBS, IBD, short bowel, hyper mobility, drugs side effects.)

White rice - Binds in stool
White bread/pasta - Low in fibre

Limit fruit to 3 portions per day

Avoid caffeine, sorbitol, fatty or spicy foods and fizzy drinks.

Consider probiotics to reinstate a balanced intestinal flora

46
Q

What lifestyle things can you do to reduce constipation?

A

Drink more water

Increase fibre intake - wholegrain foods, fruit and veg, nuts, pulses

Regular exercise

Toilet routine (same each day) and positioning

47
Q

What medications can you get for constipation?

A

Laxatives
(osmotic, stimulants, bulk forming, stool softeners)

Enemas
(Osmotic / stimulants)

48
Q

Give examples of osmotic laxatives

A

Lactulose
Moviol
Cosmocol

49
Q

How do osmotic laxatives work?

A

Increase the amount of fluid int he large bowl by:
Drawing fluids in (lactulose)
OR
Retaining the fluids they came with (Macrogols)

50
Q

Give examples of stimulant laxatives

A 
Bisacodyl 
Sodium pocosulphate 
Senna
Co-Danthromer 
Docusate Sodium 
Glycerin
51
Q

How do stimulant laxatives work?

A

Increase intestinal motility

May be given orally to PR

Docusate sodium acts as stimulant and stool softener

Glycerin suppositories cause rectal irritation and lubrication

52
Q

Give examples of bulk forming laxatives

A

Basically medicine fibre

Ispaghula
Methylcellulose

53
Q

Give examples of stool softeners

A

Docusate sodium
Glycerin suppositories
Arachis oil
Liquid paraffin

54
Q

How do stool softeners work?

A

Decrease surface tension of stool

Increase penetration of fluid into stool

55
Q

What is vomiting?

A

Involuntary, forceful expulsion of gastric contents through the mouth

56
Q

What happens when we vomit?

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
57
Q

What things can make the vomiting centre (chemoreceptor trigger zone / CTZ) go?

A

Sensory afferents via midbrain
Vestibular nuclei
Direct triggers
Visceral afferents from gut

Semester 4 - Clinical Pharmacology And Therapeutics (26 decks)

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