W2 Pharmacology of intestinal motility

Question 1

What is vomiting

Answer 1

vomiting is a defence mechanism which originates from the vomiting/emetic brain centre in the brain stem

Question 2

Causes on nausea and vomiting

Answer 2

anxiety, motion sickness, migraine, pregnancy, drug side effects

Question 3

contents and function of CTZ

Answer 3

Chemoreceptor trigger zone contains 5HT3 receptors and D2 receptors. Main sight for detecting emetic stimuli.

Question 4

Vagal afferents function

Answer 4

convey signals from the gut to the brainstem (to vomiting centre)

Question 5

higher cortical centre function

Answer 5

pain, repulsive sights and smells, emotional factors

Question 6

enterochromaffin cells function in N+V

Answer 6

sense gut toxins

Question 7

Vestibular nuclei function

Answer 7

input from labyrinth

Question 8

what are the main receptors in nausea and vomiting

Answer 8

5HT receptors
Dopamine
ACh

Question 9

Where do anti-histamine act

Answer 9

H1 receptors at higher cortical centres

Question 10

where does hyoscine act

Answer 10

M1 receptors of vestibular nuclei

Question 11

where does phenothiazines act

Answer 11

D2R, CTZ

Question 12

Were does metoclopramide act

Answer 12

D2R, CTZ and stomach

Question 13

where does domperidone act

Answer 13

D2R, CTZ

Question 14

where does droperidol and haloperidol act

Answer 14

D2R, CTZ

Question 15

where does granisteron act

Answer 15

S-HT3 receptors, CTZ and stomach

Question 16

where does ordansetron act

Answer 16

S-HT3 receptors, CTZ and stomach

Question 17

where does palosetron act

Answer 17

S-HT3 receptors, CTZ and stomach

Question 18

where does nablione act

Answer 18

CB1R, stomach

Question 19

where does aprepitant and fosaprepitant act

Answer 19

NK1R, stomach

Question 20

name the categories of anti-emetic drugs

Answer 20

anti-histamines
antimuscarinics
5HT3-receptor antagonists 
Dopamine receptor antagonists
Neurokinin receptor 1 antagonists

Question 21

Examples of anti-histamine drugs,
their action,
what they are indicated for
side effects

Answer 21

cyclizine, promethazine, diphenhydramine
antagonise on H1R in brain
indicated for N+V due to motion sickness
S/E= sedation

Question 22

example of anti-muscarinic drug
their action
indicated for
side effects

Answer 22

scopolamine (hyoscine)
muscarinic AChR antagonists on brain
indicated for motion sickness
S/E= dry mouth, tachycardia, constipation

Question 23

examples of 5HT3R antagonists
where they act
side effects

Answer 23

• ondansetron, granisetron, palonosetron
• act on 5HT3R in CTZ in medulla of hindbrain and in the GI tract
• constipation, diarrhoea, headache

Question 24

examples of Dopamine receptor antagonists (what does the drug name end in?)
actions
side effects

Answer 24

Chloropromazine, Droperidol, haloperidol, prochlorperazine, meoclopramide, domperidone
drug name ends in azine, idol, ect
acts as antagonist at D2R in CTZ of medulla of hindbrain (except domperidone- difficulty crossing BB barrier) and D2R in GI tract
SE= diarrhoea, and extra-pyramidal SE (except domperidone)

Question 25

Examples of NKR1 antagonists, their actions and side effects

Answer 25

fosapepitant, aprepitant
NKR1 antagonists in GI tract and CTZ in medulla of hindbrain blocking effect of substance P
SE= constipation and headache

Question 26

Two types of drugs which effect gut motility

Answer 26

anti-diarrhoeal drugs and laxatives

Question 27

name the 3 types of laxatives and their action

Answer 27

• ispaghula husk: ‘bulk forming’ laxative, bulk leads to peristaltic reflexes
• lactulose: ‘osmotic laxative’ - osmotic load leads ot increase fluid in the bowel
• senna: ‘stimulant purgative’- increases electrolyte and h20 secretion from rectal mucosa and stimulates myenteric plexus- peristaltic reflex

Question 28

name the 2 anti-diarrhoeal drugs used and their action
what are they sometimes combined with
side effects of anti-diarrhoeal drugs

Answer 28

• loperamide, diphenoxylate -opiates which bind to u-opiate receptors
• electrolyte replacements
• sometimes combined with atropine
• constipation, sedation, respiratory depression