Pharmacology of Nausea and Vomiting

Question 1

Vomiting/nausea may be caused by?

Answer 1

Anxiety
Motion sickness
Pregnancy
Side effects of drugs

Question 2

What is nausea?

Answer 2

Unpleasant urge to vomit

Question 3

What is vomiting and it’s medical name?

Answer 3

Emesis
Forceful expulsion of stomach contents
Defence mechanism triggered by emetic centre in brain stem

Question 4

Retching?

Answer 4

Repetitive reverse peristalsis

Question 5

What is regurgutation?

Answer 5

Effortless movement of food contents

Stomach acid coming back into the mouth

Question 6

Pathway of vomiting?

Answer 6

Systemic toxins in gut lumen
>
Enterochromaffin cells in mucosa release mediators like 5HT
>
Depolarisation of sensory afferent terminals in mucosa (5HT3 receptors)
>
AP discharge in vagal afferents to brainstem
>
Coordination of vomiting by vomiting centre

Question 7

What is the vomiting centre?

Answer 7

Group of interconnected neurones within medulla

Question 8

What are the events of vomiting?

Answer 8

• Sphincters are relaxed
• Retrograde contractions from ileum to stomach take place
• Preceeded by salivation, sweating, elevated HR and aspiration

Question 9

Where is the CTZ and what is it?

Answer 9

Chemoreceptor trigger zone

located next to vomiting centre (medulla) - opposite side of brain barrier from VC

Question 10

What is the chemoreceptor trigger zone triggered by?

Answer 10

Cancer chemotherapy opiods+ chemo & radiotherapy gastroenteritis

Question 11

What acts on the CTZ?

Answer 11

DA antagonists

5HT3 antagonist

Question 12

What is the VC?

Answer 12

Vomiting centre

Question 13

What is the VN?

Answer 13

Vestibular nuclei

Question 14

What does VN do?

Answer 14

Acts on VC in motion sickness

Question 15

What drugs act on the VN?

Answer 15

H1 antagonist

Anti-muscarinic drugs

Question 16

Examples of anti-emetics?

Answer 16

Antihistamines 
5HT3 receptor antagonists
Dopamine Receptor Antagonists 
Neurokinin- 1 Receptor Antagonists 
Metoclopramide

Question 17

Examples of anti-histamines?

Answer 17

Antagonists at histamine H1 receptors in brain (blocks H1 receptors in VN)

Question 18

What are antihistamiines useful for?

Answer 18

Motion sickness

Question 19

Side effects of antihistamines?

Answer 19

Sedation

Question 20

What do antimuscarinics do?

Answer 20

Act as antagonists at muscarinic ACh M1 receptors in brain ( block muscarinic receptors in VN and VC)

Question 21

What are antimuscarinics used for?

Answer 21

Motion sickness

Question 22

Examples of anti-muscarinic drugs?

Answer 22

Scopolamine (hyoscine)

Question 23

Side effects of anti-muscarinic drugs?

Answer 23

Dry mouth
Tachycardia
Constipation

Question 24

Examples of 5HT3 receptor antagonists?

Answer 24

Granisetron
Ondansetron
Palonosetron

Question 25

What do 5HT3 receptor antagonists do?

Answer 25

Block 5HT3 receptors in the GIT and CNS

Question 26

What are 5HT3 receptor antagonists used for?

Answer 26

Good for chemo induced nausea & vomiting Radiation induced emesis Post-operative nausea/vomiting

Question 27

Side effects of 5HT3 receptor antagonists?

Answer 27

Constipation Diarrhoea Headache

Question 28

Examples of dopamine Receptor antagonists? (DA)

Answer 28

``` Prochloroperazine Droperidol Haloperidol Trifluoperazine Chloropromazine Metoclopramide ```

Question 29

What do Dopamine receptor antagonists do?

Answer 29

Block D2 receptors in the CTN of he medulla and D2 receptors in the GIT

Question 30

What are Dopamine receptor antagonists used for?

Answer 30

Nausea & vomiting associated with neoplastic disease Radiation sickness Drug-induced emesis

Question 31

Side effects of Dopamine receptor antagonists?

Answer 31

Diarrhoea | Extrapyramidal side effects

Question 32

Examples of Neurokinin 1 receptor Antagonists?

Answer 32

Fosaprepitant | Aprepitant

Question 33

How do Neurokinin 1 receptor antagonists work?

Answer 33

Block NK1 receptors in GI tract and the CTZ of medulla in hindbrain- blocking side effects of substance P (which evokes vomiting)

Question 34

Side effects of Neurokinin receptor antagonists?

Answer 34

Constipation | Headache

Question 35

Examples of anti-diarrhoeal drugs?

Answer 35

Loperamide | Diphenoxylate

Question 36

What are anti-diarrhoeal drugs?

Answer 36

Electrolyte replacements

Question 37

Side effects of anti-diarrhoeal drugs?

Answer 37

Constipation Sedation Respiratory depression