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Flashcards in Anti-Emetics Deck (33)
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1

State the 4 major classes of anti-emetic drugs.

H1 receptors
Dopamine (D2) receptor antagonists
Muscarinic receptor antagonists
Serotonin (5-HT3) receptor antagonists

2

What types of receptors in the stomach transmit signals to the vomiting centre and chemoreceptor trigger zone?

Chemoreceptors and Mechanoreceptors

3

What is special about the location of the CTZ and vomiting centre?

It is located in a part of the brain that has a very porous blood brain barrier
So the CTZ and vomiting centre act as an early warning system to protect the brain from toxin damage

4

What are the uses of promethazine?

Motion sickness

5

Give of example of dopamine receptor antagonists.

Metoclopramide

6

Give an example of a muscarinic receptor antagonist.

Hyoscine

7

What is the mode of action of muscarinic receptor antagonists in anti-emetics?

Act centrally on the CTZ, vestibular nuclei and vomiting centre to block the activation of the vomiting centre

8

What is hyoscine used for?

Prevention of MOTION SICKNESS

9

Give an example of a serotonin receptor antagonist.

Ondansetron

10

What is the mode of action of serotonin receptor antagonists?

Act to block transmission in visceral afferents and CTZ

11

What is the main use of serotonin receptor antagonists as an anti-emetic?

MAIN USE: preventing anti-cancer drug induced vomiting (especially cisplatin)

12

Example of treatment that can cause vomiting

Cisplatin for lung cancer-chemotherapy induced nausea and vomiting

13

Pathophysiology of cisplatin

Toxic to ECL cells in the stomach which cause release of free radicals. These free radicals cause an excessive serotonin release. The serotonin activates 5-HT3A receptors on nerve fibres to Chemoreceptor Trigger Zone

14

Effect of activation of CTZ

Activates fibres to vomiting centre which induces feeling of vomiting

15

Combined therapy for CINV

Ondensatron- 5HT3A antagonist
Glucocorticoids- reduce free radicals
Aprepitant- neurokinin 1 therapy

16

Common presentation of afro-carribean person for vomiting

Motion sickness

17

Pathophysiology of motion sickness

Neural mismatch in the labyrinth which activates histamine receptors on vestibular nuclei. Vestibular nerve fibres then activate muscarinic receptoes on CTZ which activates muscarininc receptors in VC

18

Treatment for motion sickness

Promethazine
Hyoscine

19

What is promethazine

H1 receptor antagonist

20

Pathophysiology of gastroparesis

Delayed emptying of the stomach and reduced stomach contraction.

21

How does gastroparesis cause vomiting

Get an increase in 5-HT that activates 5-HT3A receptors on CTZ-> this activates muscarinic fibres on VC

22

Treatment of gastroparesis

Metoclopramide

23

What does metoclopramide do

D2 receptor antagonist
5-HT3A receptor antagonist - acts on CTZ

24

How is a dopamine 2 receptor antagonist useful in vomiting treatment

Stimulates gastric opening
Inhibits D2 receptors in CTZ

25

Where does CTZ recieve inputs from

Stomach
Vestibular nuclei

26

Receptors associated with CTZ

Serotonin- 5HT3A
Muscarinc 1-2
Dopamine 2

27

Receptor associated with vestibular nuclei

Histamine

28

Receptor associated with VC

Muscarinic

29

Main causes of vomiting

Cytotoxic drugs
Motion sickness
Pregnancy
GI problems
Parkinsons treatment due to dopamine

30

Side effects of muscarinic antagonists

Drowsiness
Dry mouth