Pharmacology

Question 1

Action of Histamine in HCl secretion (3)

Answer 1

Histamine is secreted by enterochromaffin-like cells in gastric glands in response to ACh stimulation
Histamine binds to H2 receptors with subsequent activation of adenylyl cyclase
The increase in cAMP increases the number of proton pumps and gastric acid secretion

Question 2

Action of ACh in HCl secretion (3)

Answer 2

ACh is released by parasympathetic cholinergic neurons
ACh binds to muscarinic (M3) ACh receptors on parietal cells with subsequent activation of PLC
This increases intracellular Ca2+ evoking cell signalling pathways, increasing the number of proton pumps and gastric acid secretion

Question 3

Action of gastrin in HCl secretion (3)

Answer 3

Gastrin is released by G cells
Gastrin binds to CCK2 receptors on parietal cells with subsequent activation of PLC
This increases intracellular Ca2+ increasing the number of proton pumps and gastric acid secretion

Question 4

Action of somatostatin in HCl secretion (3)

Answer 4

Somatostatin is secreted by D cells in gastric glands
Somatostatin binds to SST2R receptors, inhibiting adenylyl cyclase and histamine release - No H2 receptor activation
The decrease in cAMP decreases gastric acid secretion from parietal cells

Question 5

Antacids function

Answer 5

Reduces symptoms of excessive gastric acid secretion by buffering HCl

Question 6

Antaacids examples (2)

Answer 6

Gaviscon

Sodium Alginate

Question 7

NSAIDs action in HCl secretion (2)

Answer 7

Disrupts action and production of prostaglandins by inhibiting COX-1
Decreased prostaglandins causes histamine secretion which increases HCl secretion

Question 8

Drug to counter NSAIDs action and its characteristics (4)

Answer 8

Misoprostol
Indicated for prophylaxis of NSAID-induced peptic ulcer
Side effects are abdominal pain and diarrhoea
Also induces labour

Question 9

Proton-pump inhibitors drugs and its characteristics (4)

Answer 9

Lansoprazole, Omeprazole
Irreversibly inhibit H+/K+-ATPase pump which reduce HCl secretion - Countered with more proton pumps
Indicated for benign gastric acid ulceration, NSAID-associated gastric ulceration, gastro-oesophageal reflux disease, Zollinger–Ellison syndrome
Side effects are increased stomach pH - Reduce defence against GI tract infection

Question 10

H2 receptor antagonists drugs and its characteristics (4)

Answer 10

Ranitidine, Cimetidine
Blocks H2 receptor decreasing HCl secretion
Complete block of H2 receptors results in a rapid effect
Indicated for benign gastric acid ulceration and NSAID-associated gastric ulceration

Question 11

Drugs in H.pylori infection treatment (4)

Answer 11

PPIs
Clarithromycin
Amoxicillin or Metronidazole

Question 12

Mucosal strengtheners (2)

Answer 12

Sucralfate

Bismuth chealate

Question 13

Sucralfate function

Answer 13

Provides mucosal barrier against acid and pepsin

Question 14

Bismuth chealate function and its characteristics (3)

Answer 14

Toxic towards H.pylori
Used in combination with H2 antagonists
Administered with Ranitidine

Question 15

Vomiting Mechanism is (2)

Answer 15

Defensive

Triggered by emetic centre in brain stem

Question 16

Main neurotransmitters involved in nausea/vomiting (3)

Answer 16

5-HT
Dopamine
ACh

Question 17

Chemoreceptor Trigger Zone location (2)

Answer 17

Next to emetic centre

Opposite side of brain barrier (So can be triggered by chemotherapy)

Question 18

What antagonists acts on the Chemoreceptor Trigger Zone (2)

Answer 18

5-HT3 antagonist

Dopamine antagonist

Question 19

Anti Emetic drugs (5)

Answer 19

Antihistamines 
Antimuscarinics 
5-HT3 receptor antagonists
Dopamine receptor antagonists
Neurokinin-1 receptor antagonists

Question 20

Antihistamines (4)

Answer 20

Cyclizine, Promethazine
H1 receptor antagonists in emetic centre
Indicated in motion sickness
Side effect is sedation

Question 21

Antimuscarinics (4)

Answer 21

Scopolamine (Hyoscine)
Muscarinic ACh M1 receptor antagonists in emetic centre
Indicated in motion sickness
Side effects are dry mouth, tachycardia, constipation

Question 22

5-HT3 receptor antagonists (4)

Answer 22

Ondensetron, Granisetron
Blocks 5-HT3 receptor in GI tract and CTZ
Good for chemo and post-operative induced nausea and vomiting, radiation induced emesis
Side effects are constipation, diarrhoea and headache

Question 23

Dopamine receptor antagonists (4)

Answer 23

Metoclopramide, Domperidone
Blocks D2 receptors in CTZ and GI tract
Increases gastric peristalsis and lower esophageal sphincter tone
Side effects are diarrheoa and extrapyramidal side effects (except Domperidone)

Question 24

Neurokinin-1 receptor antagonists (3)

Answer 24

Fosaprepitant, Aprepitant
Blocks NK1 receptors in CTZ and GI tract and effect of substance P
Side effects are Constipation and headache

Question 25

Drugs affecting GI motility (2)

Answer 25

Antidiarrhoeal drugs

Laxatives

Question 26

Antidiarrhoeal drugs (5)

Answer 26

Electrolyte replacement
Loperamide, Diphenoxylate - Opiates that bind to gamma-opiate receptors
Sometimes combined with atropine
High doses of Loperamide have been associated with drug abuse
Side effects are constipation, sedation, respiratory depression

Question 27

Laxatives types (3)

Answer 27

Ispaghula husk - Bulk forming laxative
Lactulose - Osmotic laxative
Senna - Increases electrolyte/water secretion