17. Upper GI Pharmacology

Question 1

Which cells release pepsinogen?

Answer 1

Chief cells

Question 2

What is mucous production stimulated by?

Answer 2

Prostaglandins

Question 3

What cells produce gastrin?

Answer 3

G cells

Question 4

What stimulates the production of gastrin?

Answer 4

AAs and peptides

Question 5

What is the function of gastrin?

Answer 5

Binds to CCK-B receptors on parietal cells

Increase pepsinogen and gastric motility

Question 6

What receptors does ACh work on in the stomach?

Answer 6

M3 on parietal cells

Question 7

What cells secrete histamine?

Answer 7

Mast cells or enterochromaffin cells

Question 8

What factors increase the secretion of histamine?

Answer 8

Gastrin and ACh

Question 9

What factors decrease acid secretion?

Answer 9

Prostaglandins E2 and I2

Somatostatin

Question 10

What is the treatment for peptic ulcers if a patient is not taking NSAIDs?

Answer 10

Test for h.pylori
+ 1 week eradication
- PPI 4-8 weeks

Question 11

What is the treatment for peptic ulcers if a patient is taking NSAIDs?

Answer 11

Stop NSAID if possible
Test for h.pylori
+ 8 weeks PPI then 1 week eradication
- PPI 8 weeks

Question 12

How is H. pylori eradicated?

Answer 12

Triple therapy:
Amoxicillin and clarithromycin/metronidazole
plus a PPI
for 1 week

Question 13

Name a PPI

Answer 13

Omeprazole

prodrug which is metabolically active at a low pH

Question 14

How does omeprazole work?

Answer 14

Blocks H+/K+ ATPase, ie no H+ for HCl acid

Question 15

What method of dosing is used for PPIs?

Answer 15

‘Step down’ start with a high dose and reduce it

Question 16

What are the side effects of PPIs?

Answer 16

C.diff
Low magnesium
B12 deficiency

Question 17

What are the indications for PPIs?

Answer 17

PUD, GORD
Prophylaxis if taking NSAIDs
Zollinger Ellison Syndrome

Question 18

Name 2 H2 receptor antagonists

Answer 18

Cimetidine

Ranitidine

Question 19

How does cimetidine work?

Answer 19

Blocks the effects of histamine, ACh and gastrin on parietal cells
> reduced pepsin secretion

Question 20

What are the side effects of cimetidine?

Answer 20

Interact with CYP450
Antiandrogenic
Ranitidine doesn’t have these effects
Both cause drowsiness

Question 21

Name 3 cytoprotective agents

Answer 21

Misoprostol
Sucralfate
Bismuth

Question 22

What is the MOA of misoprostol?

Answer 22

Synthetic prostaglandins: increase mucous production, decrease secretion by acting on parietal cells

Question 23

Which group is misoprostol used for?

Answer 23

High-risk groups taking NSAIDs

Question 24

What are the side effects of misoprostol?

Answer 24

Diarrhoea and uterine contractions (contraindicated in pregnancy)

Question 25

What is the MOA of sucralfate?

Answer 25

Binds to base of ulcer and increases prostaglandins and bicarb

Question 26

What side effect is associated with sucralfate?

Answer 26

Bezoar formation which can cause gastric blockage | Avoid by making sure well hydrated

Question 27

What is the MOA of bismuth?

Answer 27

Increase prostaglandin synthesis and bicarb and inhibits h.pylori Used in triple therapy if allergy or resistance

Question 28

What are antacids?

Answer 28

Weak bases used to neutralise gastric acid Used for symptom relief Eg. sodium bicarb, calcium carbonate, magnesium, aluminium

Question 29

What is the MOA of Gaviscon?

Answer 29

Rafting agent: floats on top of acid so it doesn't enter the oesophagus Alginate

Question 30

What is the treatment for GORD?

Answer 30

Lifestyle modification PPIs first line H2 antagonist if needed Antacids/alginates for mild symptoms

Question 31

Name 2 D2 antagonists used as anti-emetics

Answer 31

Metoclopramide | Domperidone

Question 32

What is the MOA of metoclopramide?

Answer 32

Dopamine receptor antagonist | Reduce smooth muscle relaxation at D2 receptor and inhibits ACh which increases gastric emptying

Question 33

What side effects are associated with metoclopramide?

Answer 33

Extrapyramidal: tremors, seizures

Question 34

What side effects are associated with domperidone?

Answer 34

Doesn't cross BBB so no extrapyramidal | Ventricular arrhythmia and sudden cardiac death

Question 35

What regulatory mechanisms are associated with vomiting?

Answer 35

``` Cholinergic Histamine Dopamine Serotonin Cannabinoid ```

Question 36

What are anticholinergics and antihistamines used for?

Answer 36

Motion sickness

Question 37

What side effect is associated with anti-histamines?

Answer 37

Sedation

Question 38

What are dopamine receptor antagonists, serotonin receptor antagonists and cannabinoids used for?

Answer 38

Reduce vomiting caused by chemo

Question 39

Name 2 dopamine receptor antagonists

Answer 39

Phenothiazides | Butyrophenones

Question 40

Name a serotonin receptor antagonist

Answer 40

Ondansetron

Question 41

What are the side effects associated with serotonin receptor antagonists?

Answer 41

Constipation and headache

Question 42

Name a cannabinoid

Answer 42

Nabilone

Question 43

What side effects are associated with cannabinoids

Answer 43

Drowsiness, psychotic reactions