114 - Drugs Affecting the GIT

Question 1

Things that can stimulate gastric acid secretion from antral cells

Answer 1

Gastrin (from distension of stomach)

ACh (acts on muscarinic receptors)

Question 2

What releases gastrin?

Answer 2

G cells

Question 3

Effect of gastrin on parietal cells

Answer 3

Activates H+/K+ ATPase through cAMP-mediated Ca2+ increase. Pumps H+ into stomach lumen.

Question 4

Effect of muscarinic R agonists in the stomach

Answer 4

Stimulates H+ release

Question 5

Drug that can block H+ release by parietal cells into stomach

Answer 5

Atropine (muscarinic R antagonist)

Question 6

Helicobacter pylori

Answer 6

G-.
Attaches to gastric cells, releases urease which degrades urea to ammonium hydroxide, which forms an alkaline cloud around it (protects it from stomach acid).
Inflammation stimulates G cells to release gastrin, which increases acidity of the stomach

Question 7

Common therapy for Helicobacter pylori

Answer 7

Omeprazole, clarithromucin and amoxycillin (triple therapy)

Question 8

Composiiton of stomach mucus layer

Answer 8

Mucus with bicarbonate

Question 9

Prostaglandins primarily synthesised within gastric mucus layer

Answer 9

PGE2, PHI2

Question 10

Effect of PGE2 and PGI2 on stomach
1
2
3

Answer 10

1) Decrease acid secretion.
2) Increase blood flow through gastric blood vessels, which removes H+ from stomach.
3) Increase mucus secretion.

Question 11

Things that can induce PUD (peptic ulcer disease)
1
2

Answer 11

1) NSAIDS (ibuprofen, naproxen, inhibitors of COXI)

2) H pylori

Question 12

Old therapy for peptic ulcers

Answer 12

Smooth muscle relaxants

Question 13

New therapies for peptic ulcers that stop acid production

Answer 13

1) Proton pump inhibitors

2) H2-receptor antagonists

Question 14

Example of proton pump inhibitors

Answer 14

Omeprazole, Esomeprazole (very similar)

Question 15

Proton pump inhibitor mechanism

Answer 15

Permanent inhibitor of proton pumps

Question 16

Example of H2-receptor antagonist

Answer 16

Ranitidine

Question 17

Are H2R antagonists prescription drugs?

Answer 17

No

Question 18

How do ACh and gastrin cause H+ release?

Answer 18

Stimulate ECL cells to release histidine, which stimulates H2 receptors.
H2 receptor stimulation stimulates H+/K+ ATPase

Question 19

Antacids mechanism

Answer 19

Neutralise gastric acid.

Question 20

Problem with antacids

Answer 20

Side-effects, and can cause increased H+ release into stomach.

Question 21

Examples of antacids

Answer 21

Magnesium hydroxide, carbonate, oxide, trisilicate

Question 22

Side effect of the magnesium salt antacids

Answer 22

Laxative effect

Question 23

Problems with sodium bicarbonate as an antacid

Answer 23

Can lead to alkalosis.

Na+ can lead to/exacerbate hypertension.

Question 24

Example of a cytoprotective agent

Answer 24

Sucralfate (used to treat peptic ulcers)

Question 25

Examples of spasmolytics
1
2

Answer 25

1) Hyoscine butylbromide (muscarinic antagonist)

2) Mebeverine, peppermint oil (direct spasmolytics)

Question 26

Problems with muscarinic antagonists as spasmolytics

Answer 26

SLUD bloackade (salivation, lacrimation, urination, defecation)

Question 27

Why doesn’t hyoscine butylbromide cause systemic effects?

Answer 27

Not absorbed

Question 28

Peptic ulcer treatment that increases mucous secretion, blood flow and decreases gastric acid secretion.

Answer 28

Prostaglandin E analogues

Question 29

Misoprostol

Answer 29

Prostaglandin E analogue.

Used to treat peptic ulcers.

Question 30

Problems with misoprostol
1
2

Answer 30

1) Diarrhoea and spam

2) Can terminate pregnancy

Question 31

Chemoreceptor trigger zone

Answer 31

Group of neurons in the medulla that is outside the blood brain barrier.
Detects circulating agents, stimulates vomiting centre.

Question 32

Receptors involved in stimulation of chemoreceptor trigger zone

Answer 32

Dopamine D2 receptors, 5HT3 receptors.

Question 33

What do antiemetics for nausea affect?

Answer 33

Dopamine D2 receptors, 5HT3 receptors.

Question 34

Antiemetics used for motion sickness
1
2

Answer 34

1) Histamine H1 antagonists

2) Muscarinic receptor antagonists

Question 35

Receptors involved in direct stimulation of vomiting centre

Answer 35

H1 receptors

Muscarinic receptors

Question 36

Motion sickness muscarinic receptor antagonist

Answer 36

Hyoscine hydrobromide (can cross the blood brain barrier)