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Pharmacology > Gi > Flashcards

Gi Flashcards

0
Q

How does domperidone work?

A

It works on the fourth ventricle floor (prostrema)
Increases the rate of gastric emptying
It has extensive first-pass metabolism
Given orally or rectally
It does not cross BBB so no extrapyramidal effects

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1
Q

What are the two dopamine receptor antagonists used for vomiting?

A

Metoclopramide

Domperidone

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2
Q

What are the side effects of domperidone?

A

Prolactin release so galactorrhoea

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3
Q

How does metoclopramide work?

A 
Dopamine antagonist
Acts on the floor of the fourth ventricle and also increases gastric emptying
Also has anticholinergic effects
Blocks vagal afferents
Does cross the BBB
IM/IV/oral 
half life is four hours
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4
Q

What is metoclopramide used for?

A

GI causes of nausea & vomiting
Migraines
Post op

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5
Q

What are the side effects of metoclopramide?

A

Dystonia
Extra pyradimal
Galactorrhoea

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6
Q

What is ondasteron?

A

A 5HT3 receptor antagonist

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7
Q

How does ondasteron work?

A 
It has vagal stimulation
Fourth ventricle
Vagal afferents
Oral – IV – IM
Can be enhanced by a single dose of corticosteroids
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8
Q

What can ondasteron be used for?

A

Radiation sickness
Chemotherapy
Postop

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9
Q

What are the side effects of ondasteron?

A

Headache
Flushing
Constipation

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10
Q

Give an example of an Ach antagonist

A

Hyosine

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11
Q

How does hyoscine work?

A

Anticholinergic effect direct muscarinic

Half life is two hours

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12
Q

What is hyoscine used for?

A

Motion sickness

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13
Q

How do you give hyoscine?

A

Oral

Transdermal patch but you can gain tolerance to the patch

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14
Q

What are the side effects of hyoscine?

A

Bradycardia
Gluacoma
Urinary retention

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15
Q

What is cyclizine?

A

H1 antagonist
Also an antimuscarinic
Used for acute nausea and vomiting

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16
Q

What are the ADRs of cyclizine?

A

Sedation

QT prolongation

17
Q

What medications are used for diarrhoea?

A

Anti motility
Bulk forming agents
Fluid adsorbents

18
Q

How does anti motility diarrhoeal agents work?

A

They increase anal tone and sensory defecation

They decrease bowel motility so there is more time for fluid absorption

19
Q

What is a commonly used anti motility anti diarrhoeal agent?

A

Loperamide - opioid analogue

40x more potent

20
Q

What are the ADRs of loperamide?

A

Dizzy
Drowsy
Abdominal cramps
Paralytic ileus

21
Q

How do bulk forming agents work for diarrhoea?

A

They act via water absorption and to re establish normal bowel habits
But they can also be used for constipation and therefore are useful in conditions where you get both diarrhoea and constipation eg. IBD

22
Q

Give an example of a bulk forming agent

A

Isphagula

23
Q

How do fluid adsorbents work and when are they used in diarrhoea?

A

V rarely

Absorb water

24
Q

What drug is used in IBD for diarrhoea?

A

Mebeverine reserpine derivative

25
Q

How does mebeverine reserpine derivatives work?

A

They relieve spasms
Direct effects on hyper motility
No antimuscurinic side effects
Useful with a bulk forming agent

26
Q

What treatments are there for constipation?

A 
Non pharmacological 
Bulk forming laxative 
Osmotically active laxatives 
Faecal softener 
Irritant/stimulant laxatives
27
Q

What are the non pharmacological treatments of constipation?

A

Increase fluid
Increase fibre
Exercise
Treat underlying cause

28
Q

How do faecal softeners work?

A

They lubricate faeces

29
Q

Give examples of faecal softeners

A

Glycerol

Arachis oil

30
Q

How do bulk laxatives work?

A

They are plant derived which cannot be absorbed by the GI tract
They aim to reestablish normal bowel movements
Not for use today but the next day

31
Q

What is an example of a bulk forming laxative and give an ADR

A

Isphagula

Flatulence

32
Q

What are 3 osmotically active laxatives?

A

Magnesium and sodium salts
Lactulose
Macrogols

33
Q

How do magnesium and sodium salts work?

A

Cause water retention
PR route
Quick acting
Reserve for resistant constipation

34
Q

How does lactulose work?

A

Cannot be absorbed by the GI tract
Takes 48 hours to work
Cleanes the bowel
But likely to dehydrate

35
Q

How does Macrogols work?

A

Powder - less likely to cause dehydration

2-4 days relief

36
Q

How do irritant/stimulant laxatives work?

A

They cause water and electrolyte retention which stimulates peristalsis
Used for rapid treatment
6-8 hours to work

37
Q

What are the ADRs of stimulant laxatives?

A

Colonic atony
Hypokalaemia
Abdominal cramps

38
Q

Give examples of irritant laxatives

A

Castor oils
Senna
Danthron

39
Q

How do you go about choosing a laxative?

A 
For hard stools 
- bulk
- osmotic
For soft stools 
- irritant/stimulant

Pharmacology (5 decks)

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