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MD3002 Pharmacology > Treatment of Vomiting and Gut Motility Disorders > Flashcards

Treatment of Vomiting and Gut Motility Disorders Flashcards

1
Q

What is the central neural regulation of vomitting controlled by?

A

2 seperate units both in the medulla

1) the vomitting (emetic) centre
2) The chemoreceptor Trigger Zone, CTZ (passes messages on to the vomitting centre)

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2
Q

Where are the vomiting centre and CTZ located?

A
  • CTZ is located posterior to vomitting centre in area postrena and area of the 4th ventricle
  • Both in medulla
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3
Q

What is the vomiting centre?

A
  • Collection of multiple sensory, motor and control nuclei
  • Mainly in the medullary and pontile reticular formation, also extending into spinal cord
  • Receive nerve impulses from both vagal and sympathetic afferent nerve fibres
  • Responds to the incoming signals to coordinate emesis
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4
Q

What is the Chemoreceptor Trigger Zone?

A
  • Sensitive to chemical stimuli and is the main site of action of drugs which stimulate vomiting
  • The CTZ is also concerned with the mediation of motion sickness
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5
Q

WHat is the primary origin of motion sickness stimuli?

A

Vestibular apparatus

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6
Q

What area do medications have the greatest affect on vomitting?

A

Chemoreceptor Trigger Zone

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7
Q

Describe the pathway for motion sickness

A

Vestibular labyrinth -> Vestibular nuclei (brain stem) -> cerebellum -> CTZ -> Vomiting centre -> Vomit

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8
Q

What can labyrinthitis cause?

A

Vomitting

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9
Q

What can trigger nausea/vomiting?

A
  • Stimulation of the sensory nerve endings in the stomach and duodenum
  • Stimulation of the vagal sensory endings in the pharynx
  • Drugs or endogenous emetic substances
  • Disturbances of the vestibular apparatus
  • Various stimuli of the sensory nerves of the heart and viscera
  • A rise in intracranial pressure
  • Nauseating smells, repulsive sights, emotional factors
  • Endocrine factors
  • Migraine
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10
Q

What is nausea?`

A
  • Feeling of wanting to vomit
  • Associated with autonomic effecrs: salivation / pallor / sweating
  • Often pro-drome of vomiting
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11
Q

What is retching?

A
  • Strong involrntary effort to vomit

- Unproductive

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12
Q

What is vomiting?

A

Expulsion of gastric contents through the mouth

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13
Q

What can projectile vomiting be due to?

A

Suggestive of gastric outlet or upper GI obstruction

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14
Q

What can haematemesis be due to?

A

Vomiting fresh or altered blood (coffee-grounds) e.g oesophageal varices, bleeding gastric ulcer

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15
Q

What can early-morning vomiting be due to?

A
  • Pregnancy
  • Alcohol dependance
  • Some metabolic disorders (uraemia)
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16
Q

What are the potential indications for anti-emetic drugs?

A
  • Severe vomiting during pregnancy / hyperemesis gravidarum (when dehydration becomes a severe factor)
  • Postoperative nausea and vomitting
  • Motion sickness
  • Other vestibular disorders
  • N/V induced by cytotoxic chemotherapy
  • Paliative care
  • N/V associated with migraine
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17
Q

What are some types of anti-emetic?

A
  • Antihistamines (H1)
  • Antimuscarinics (M1)
  • Dopamine antagonists (D2)
  • 5HT3 antagonists
  • Neurokinin1 receptor antagonists
  • Synthetic canabinoids (CB1)
  • Steroids
  • Other neuroleptics
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18
Q

What receptor antagonists are antihistamines?

A

H1 histamine receptor antagonists

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19
Q

What are antihistamines useful for treating?

A

Motion sickness + vestibular disorders

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20
Q

What can be the side-effects of of antihistamines?

A

Drowsiness and anti-muscarinic effects

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21
Q

What are some examples of antihistamines?

A
  • Cinnarizine; motion sickness, vestibular disorders
  • Cyclizine; motion sickness
  • Promethazine; severe morning sickness
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22
Q

What is an example of an antimuscarinic useful for treating motion sickness?

A

Hyoscine Hydrobromide

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23
Q

What are the side effects of anti-muscarinics?

A
  • Constipation
  • Transient bradycardia
  • Dry mouth
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24
Q

What do antimuscarinics block?

A

Muscarinic receptor-mediated impulses from the labyrinth and from visceral afferents

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25
Q

What form are antimuscarinics given in?

A

Patches as well as tablets

26
Q

What do Dopamine (D2 receptor antagonists work against?

A
  • CTZ-triggered vomiting but not stomach-induced vomiting

- Act centrally as dopamine antagonists on the CTZ

27
Q

What are some examples of Dopamine (D2) receptor antagonists?

A 
- The phenothiazines and related drugs 
These are also classed as neuroleptics/antipsychotics 
Chlorpromazine 
Prochlorperazine 
- Domperidone 
- Metoclopramide (prescribed a lot)
28
Q

What can be the side-effects of Dopamine (D2) receptor antagonists?

A
  • Can be quite severe
  • Can have anti-psychotic medication side-effects e.g movement disorders, tick disorders
  • Can last after medication stopped
29
Q

What are 5HT3 antagonists often used for?

A

Palliative care and chemotherapy (cytotoxics)

30
Q

What receptors do 5HT3 antagonists block?

A

5HT3 receptors in GI tract and in the CNS

31
Q

Give an example of a 5HT3 antagonist

A

Ondansetron

32
Q

When would a Neurokinin receptor antagonist be used?

A

Adjunct to dexamethasone and a 5HT3 antagonist in preventing N/V associated with chemotherapy
- Sustained vomitting unresponsive to standard measures

33
Q

What is an example of a Neurokinin receptor antagonist?

A

Aprepitant

34
Q

What receptors do synthetic cannabinoids act on?

A

CB1 receptors

35
Q

When are synthetic cannabinoids used?

A

For N/V caused by chemo unresponsive to conventional anti-emetics

36
Q

What are common side-effects of synthetic cannabinoids?

A

Drowsiness/dizziness

37
Q

When are steroids (e.g dexamethasone) used to treat vomitting?

A
  • Can be used alone to treat vomiting associated with cancer chemotherapy, or in conjunction with other antemetics
  • Often used to shrink tumours not just anti-emetic effect also produce appeitie stimulation
38
Q

What can happen to the colon as a result of constipation?

A

Colon distention

39
Q

Why is a PR examination extremely important when a patient presents with diahrohea?

A

Could really be constipation and hardened stool blocking the anal canal allowing only for liquid stool to pass through

40
Q

What chart allows us able to be able to analyse the consistancy of stool?

A

Bristol stool chart (type 1 - 7)

41
Q

What should you do before prescribing laxatives?

A
  • Ensure the problem is actually constipation
  • Check the patient’s “norm”
  • Try to reverse the cause; including diet/lifestyle changes (e.g prunes/ornages/liquids in children)
42
Q

What are the types of laxatives?

A
  1. Bulk-forming laxatives
  2. Stimulant laxatives
  3. Faecal softeners
  4. Osmotic laxatives
  5. Peripheral opoid-receptor antagonists
43
Q

Give an example of a bulk -forming laxative?

A

Ispaghula husk

44
Q

Give an example of a stimulant laxative

A

Senna

45
Q

Give an example of a faecal softner

A

Docusate

46
Q

Give an example of an osmotic laxative

A

Lactulose

47
Q

Give an example of a peripheral opoid receptor antagonist

A

Methylnatrexone bromide

48
Q

What are the approaches for treatment of ACUTE diarrhoea?

A
  1. Maintanence of fluid and electrolyte balance e.g oral rehydration therapy
  2. Antimotility drugs
  3. Antispasmodics (reduce SM tone) e.g hyoscine butylbromide (buscopan), mebeverine
  4. Occasionally antibacterial agent is indicated e.g. systemic bacterial infection
49
Q

Give an example of an antimotility agent used to treat chronic diarrhoea

A

Loperamide (imodium)

50
Q

Give an example of an adsorbent used to treat chronic diarrhoea?

A

Kaolin, light

51
Q

Give an example of a bulk forming drug (useful in controlling diarrhoea assoc. with diverticular disease) used to treat chronic diarrhoea?

A

Ispaghula

52
Q

What are the types of drugs used to treat chronic diarrhoea?

A
  • Antimotility agents (loperamide/imodium)
  • Adsorbents (NB not for acute) kaolin, light
  • Bulk forming drugs (useful in controlling diarrhoea assoc. with diverticular disease); ispaghula
53
Q

What can be used to treat both diarrhoea and constipation?

A

Bulk-forming ispaghula

54
Q

What is contained in bile?

A
  • Bile salts
  • Bilirubin
  • Cholesterol
  • Lecithin
  • Plasma elctrolytes
55
Q

What hormone stimulates gallbladder emptying?

A

Cholecystokinin (CCK)

56
Q

What percentage of Gallstones in the UK are cholesterol stones?

A

80%

57
Q

How are gallstones usually treated?

A

Laparoscopic cholecystectomy

58
Q

What is used to dissolve gallstones?

A

Ursodeoxycholic acid (mainly if mild symptoms and not amenable to other treatment)

59
Q

What is prescribed to treat the pain associated with biliary colic?

A
  • Opoids (such as morphine or pethidine), given parenterally and/or diclofenac (NSAID) by suppository
60
Q

Why is the parenteral/rectal route chosen over the oral route when treating bilary colic and acute cholecystitis?

A

Overcomes difficulties in absorption caused by vomiting

61
Q

What is colesytamine?

A
  • Anion-exchange resin
  • Reducing gallstones can bind with bile-acids encourages liver to reduce cholesterol
  • Relieves pruritus associated with partial biliary obstruction and primary biliary cirrhosis
  • Can also be used in some instances of diarrhoea e.g Crohn’s disease related
  • Also can be used in hypercholesterolaemia

MD3002 Pharmacology (7 decks)

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