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Gastrointestinal > Pharmacology > Flashcards

Pharmacology Flashcards

(49 cards)

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1
Q

Describe the pathway of H+ and Cl- leaving parietal cells

A
  • Cl- enters parietal cell from blood via chloride-bicarbonate exchanger
  • Cl- leaves parietal cell to gastric lumen via chloride-potassium symporter
  • H+ leaves parietal cell via H+/K+ ATPase into gastric lumen
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2
Q

What is the role of carbonic anhydrase in parietal cells?

A

Converts CO2 and H2O into H2CO3 (carbonic acid)

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3
Q

What is the role of carbonic acid in parietal cells?

A

Dissociates into HCO3- ions for the chloride-bicarbonate exchanger and H+ ions for HCl

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4
Q

Which cells in the gastric pit form histamine?

A

Enterochromaffin-like cells

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5
Q

Describe the mode of action of histamine on gastric acid secretion

A
  • Histamine acts on H2R receptors
  • Causes an increase in adenylyl cyclase
  • Leads to increased cAMP production
  • increases the number of proton pumps
  • increases gastric acid secretion from parietal cells
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6
Q

What stimulates histamine release?

A

Acetylcholine via parasympathetic innervation

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7
Q

Describe the mode of action of acetylcholine on gastric acid secretion

A
  • ACh activates muscarinic M3 receptors on parietal cells
  • Activates phospholipase C causing increased Ca2+
  • This causes increase in number or proton pumps
  • Causes increased gastric acid secretion
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8
Q

Describe the mode of action of gastrin on gastric acid secretion

A
  • Gastrin from G cells activates CCK2 receptors
  • Causes an increase in Ca2+ via PLC
  • Causes an increase in proton pump numbers
  • Causes increased gastric secretion
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9
Q

Describe the mode of action of somatostatin on gastric acid secretion IN PARIETAL CELLS

A
  • Somatostatin from D cells activates SST2 receptors on parietal cells
  • Inhibits AC, decreases cAMP, decreases number of proton pumps
  • Causes decrease in gastric acid secretion
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10
Q

Describe the mode of action of somatostatin on gastric acid secretion IN ENTEROCHROMAFFIN-LIKE CELLS

A
  • Activates SST2 receptors
  • Opposes ACh stimulation: inhibits histamine
  • decreased histamine decreases gastric secretion
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11
Q

What are the active components in antacids?

A

Sodium bicarbonate, NaHCO3
Calcium carbonate, CaCO3
Sodium alginate

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12
Q

How do antacids work?

A

Their active components are bases which dissociate and react with H+ to buffer excess acid

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13
Q

What are NSAIDs?

A

Non steroidal anti-inflammatory drugs, can cause NSAID-induced gastric ulceration

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14
Q

Describe the mechanism of action of NSAIDs on gastric acid secretion

A
  • NSAIDs inhibit cyclooxygenase 1, inhibiting prostaglandins production
  • Decreased prostaglandins causes increased histamine release
  • causes increased HCl secretion
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15
Q

What is the role of prostaglandins in gastric acid secretion?

A

Inhibits histamine, causing decreased HCl secretion

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16
Q

What is the drug indicated for prophylaxis of NSAID-induced peptic ulcers?

A

Misoprostol, an analogue of prostaglandin E1

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17
Q

What are the side effects of misoprostol?

A

Abdominal pain, diarrhoea, can induce labour

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18
Q

Name 3 proton pump inhibitors

A

Lansoprazole
Omeprazole
Pantoprazole

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19
Q

How do proton pump inhibitors work?

A

They bind irreversibly to H+/K+ ATPase, directly decreasing HCl secretion

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20
Q

What conditions indicate PPIs?

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A

Benign gastric acid ulceration
NSAID-induced gastric ulceration
gastro-oesophageal reflux disease
Zollinger-Ellison syndrome

21
Q

What is a side effect of PPIs?

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A

Increased stomach pH making patients more susceptible to infections in the GI tract

22
Q

Name 3 histamine H2 receptor antagonists

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A

Ranitidine
Cimetidine
Famotidine

23
Q

How do H2 receptor antagonists work?

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A

Block H2R on parietal cells, causing decreased HCl secretion

24
Q

Which conditions indicate H2 receptor antagonists?

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A

Benign gastric acid ulceration

NSAID-induced gastric ulceration

25
How does H. pylori cause peptic ulcers?
HP migrates into mucus layer Damages mucus cells Depletion of mucus layer Exposure of mucosa to low pH causes ulcers
26
How are HP peptic ulcers treated?
PPIs | Antibiotics: clarithromycin and amoxicillin or metronidazole
27
What types of anti-emetics are there?
``` Histamine H1 receptor antagonists Antimuscarinics 5-HT3 receptor antagonists Dopamine receptor antagonists Neurokinin-1 receptor antagonists ```
28
Name 3 H1 receptor antagonists
Cyclizine Promethazine Diphenhydramine
29
Name an antimuscarinic
Scopolamine (hyoscine)
30
Name 3 5-HT3 receptro antagonists
Ondansetron Granisetron Palonosetron
31
Name 4 dopamine receptor antagonists
Chlorpromazine Haloperidol Prochlorperazine Metoclopramide (also a 5-HT3 RAnt at high conc)
32
Name 2 neurokinin-1 receptor antagonists
Fosaprepitant | Apreptant
33
What areas of the brain and body are involved in vomiting signalling?
- Chemoreceptor trigger zone (CTZ) in brain - Vomiting centre, dorsal to CTZ - Cortical areas (anxiety) - Vestibular nuclei (motion sickness) - Plexuses in the gut
34
Where is information about vomiting coordinated in the brain?
Psychological, vascular, and gastric information is coordinated at the chemoreceptor trigger zone and vomiting centre
35
What drugs are indicated for motion sickness?
Histamine H1 receptor antagonists and antimuscarinics
36
What are the side effects of H1 receptor antagonists?
Sedation
37
What receptor do antimuscarinics work on?
Muscarinic cholinergic M1 receptors in the brain
38
What are the side effects of antimuscarinics?
Dry mouth Tachycardia Constipation
39
Where do 5-HT3 receptor antagonists affect?
The CTZ in the medulla | The enteric plexuses
40
What are the side effects of 5-HT3 receptor antagonists?
Constipation Diarrhoea Headache
41
Where do dopamine receptor antagonists act?
At D2 receptors in CTZ and D2 receptors in GI tract
42
What are the side effects of dopamine receptor antagonists?
Diarrhoea | Extrapyrimidal side effects
43
Where do NK-1 receptor antagonists act and what are their side effects?
Neurokinin-1 receptors in the CTZ and GI tract Side effects: Constipation Headache
44
What is the first line of treatment for diarrhoea?
Electrolyte replacements
45
Name 2 antidiarrhoeal drugs
Loperamide Diphenoxylate (opiates)
46
Give the side effects for antidiarrhoeal drugs
Constipation Sedation Respiratory depression Can be addictive at higher doses
47
How do antidiarrhoeal drugs work?
Inhibit gut motility - agonists of opiate receptors
48
Name 3 laxatives
Lspaghula husk Lactulose Senna
49
How do laxatives work?
By stimulating peristalsis, and/or increasing water/electrolyte secretion

Gastrointestinal (5 decks)

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