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BMS13 > Pharmacology of Gastric Acid Control > Flashcards

Pharmacology of Gastric Acid Control Flashcards

1
Q

What are ulcers?

A

Chronic, usually solitary lesions/sores in areas of the GI tract exposed to acids/peptic juices

Display spontaneous relapse and remission

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2
Q

Where are ulcers most commonly found?

A

Duodenum

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3
Q

How much more common are duodenal ulcers than gastric ulcers?

A

4 times

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4
Q

What are the symptoms of ulcers? (5)

A

Abdominal pain - typically an epigastric burning sensation

Usually nocturnal pain

Heartburn

Bloating

Duodenal ulcer pain relieved by eating

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5
Q

What are the three complications which can arise from ulcers?

A

Penetration

Perforation

Upper GI bleeding

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6
Q

Does acid hypersecretion cause ulcers?

A

Only in Zollinger-Ellison syndrome

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7
Q

What is Zollinger-Ellison syndrome?

A

Rare, gastrin-producing tumour of pancreas or duodenum causing oversecretion of acid

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8
Q

Does smoking cause ulcers?

A

No, risk factor - interferes with healing/blood flow

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9
Q

By how much does smoking increase the risk of getting ulcers?

A

50% increase

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10
Q

What is the main bacteria which is associated with ulcers?

A

Helicobacter pylori

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11
Q

Does Helicobacter pylori cause ulcers?

A

Causes chronic gastritis which weakens the mucosal barrier allowing ulcers to form

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12
Q

What drugs can cause ulcers?

A

Aspirin and NSAIDS

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13
Q

What is the main type of ulcer caused by NSAIDs?

A

Gastric

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14
Q

What percentage of ulcers are idiopathic?

A

20%

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15
Q

How do NSAIDs and aspirin cause ulcers?

A

Inhibit prostaglandin production which weakens the mucosal barrier allowing ulcers to form

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16
Q

What must be balanced to prevent ulcers?

A

Mucosal defense

Acid/pepsin secretion

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17
Q

What are the usual characteristics of gastric ulcers?

A

Helicobacter pylori infection of gastric corpus

Low-normal levels of acid with defect in gastric mucosal defense

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18
Q

What are the usual characteristics of duodenal ulcers?

A

Helicobacter pylori infection of pyloric antrum

Increased acid/pepsin secretion causing gastric metaplasia of duodenum which allows infection by H. pylori

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19
Q

What type of tissue can Helicobacter pylori infect?

A

Gastric

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20
Q

What affects the progression of acute gastritis to chronic gastritis?

A

Host factors

Strain of Helicobacter pylori

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21
Q

What does antral predominant gastritis lead to?

A

Duodenal ulcers

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22
Q

What does multifocal atrophic gastritis lead to?

A

Gastric ulcers

Gastric cancer

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23
Q

Why is there often low levels of acid production with gastric ulcers?

A

Multifocal atrophic gastritis - ongoing inflammation causes gastric mucosa to be replaced by intestinal and fibrous tissue

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24
Q

Are those in the age group 20-40yo more likely to get gastric ulcers or duodenal ulcers?

A

Duodenal ulcers

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25
What is Helicobacter pylori?
Spiral-shaped bacterium which causes chronic gastritis Incidence increases with age
26
What does Helicobacter pylori do?
Grows on enterocyte surface beneath mucus Increases secretion of gastrin and pepsin May produce toxins which damage the mucosa
27
What is the Cag pathogenicity island?
Collection of genes coding for CagA and a type IV secretion system Makes some strains of H. pylori especially pathogenic
28
What is CagA?
Cytoskeleton-disrupting protein
29
What does a type IV secretion system do?
Injects CagA into epithelial cells
30
How does Helicobacter pylori protect itself from acid?
Secretes a urease Converts endogenous urea to HCO3 and CO2 = alkaline bubble
31
How do we test for H. pylori?
Test for antigens in stool samples Test for antibodies in blood samples
32
How does histamine affect parietal cells?
Binds H2 receptors Increase cAMP and phosphorylation Increase acid production
33
How do ACh and gastrin affect parietal cells?
Increase intracellular Ca to increase acid production
34
Which prostaglandin is prominent in the mucosal defence system?
PGE2
35
What does PGE2 do?
Bind to EP3 receptors - On mucus-producing cells to stimulate release of HCO3 and mucus - On parietal cells to suppress HCl secretion Vasodilatation
36
Give an example of a proton pump inhibitor.
Omeprazole Esomeprazole
37
What do proton pump inhibitors do?
Irreversibly block parietal cell H/K-ATPase
38
What is the mechanism of proton pump inhibitors? (4)
Inactive pro-drugs at neutral pH Absorbed in SI and move via blood to accumulate in oxyntic glands Converted to sulfenamides at pH<3 React covalently with sulfhydryl groups on ATPase
39
Why is only one pill of omeprazole required per day?
Proton pump inhibitors irreversibly block H/K-ATPase Cells must make more H/K-ATPase to secrete acid
40
What are the adverse effects of PPIs?
Uncommon but long-term use can cause osteoporosis and increased risk of serious cardiac events Withdrawal can cause rebound acid hypersecretion
41
Give an example of a H2 receptor blocker.
Famotidine Ranitidine Cimetidine
42
What do H2 receptor blockers do?
Selectively block parietal cell H2 receptors to decrease acid production
43
What is the adverse effect associated with cimetidine?
Inhibits multiple cytochrome P450s Retards metabolism of a large number of widely used drugs such as nifedipine and warfarin
44
Why was ranitidine withdrawn in October 2019?
NDMA contamination (potential carcinogen)
45
Which drugs enhance mucosal protection? (3)
Bismuth chelate Sucralfate Misoprostil
46
What does bismuth chelate do? (3)
Coats ulcer to protect from gastric juices and promotes healing Stimulates secretion of mucus, PG, HCO3 Chemotherapeutic effects against H. pylori
47
What is sucralfate?
Aluminium hydroxide/sulfated sucrose complex
48
What type of ulcers is sucralfate used for?
Duodenal ulcers not related to NSAID use Stress ulcers
49
What is the mechanism of sucralfate?
Negative sulfated sucrose (dissociated from complex) binds HCl to form a viscous adhesive which binds positive groups in the ulcer crater This buffers acid and stimulates secretion of mucus, PG and HCO3 Decreases number and adherence of H. pylori
50
How does sucralfate affect other drugs?
Decreases absorption of some drugs like antibiotics
51
What is misoprostil?
Stable PGE1 analogue which heals and prevents NSAID-induced damage (when taken with NSAID)
52
What are the adverse effects of misoprostil?
Diarrhoea Abdominal cramps Uterine contractions - avoid in pregnancy
53
Why is antimicrobial therapy sometimes used when treating ulcers?
Eradicate H. pylori and prevent ulcer relapse
54
How is antimicrobial therapy often used in ulcer treatment?
In combination with H2 blocker or PPI (increased pH to stabilise antibiotic) 2 weeks typically
55
What is gastro-oesophageal reflux disease?
Reflux of stomach acid back into oesophagus
56
What are the symptoms of GORD?
Pain (oesophageal) Oesophagitis Heartburn Bad taste in mouth
57
What is heartburn?
Retrosternal burning pain brought on by meals or lying flat
58
What can increase the risk of developing GORD?
Transient lower oesophageal sphincter relaxation or atonic LOS Increased intra-abdominal pressure due to obesity/pregnancy/heavy meals
59
Why does GORD often worsen during sleep?
Normal defence mechanisms less active (salivation and swallowing)
60
How can GORD affect the oral cavity?
Tooth erosion
61
How does GORD cause tooth erosion?
Acid removes pellicle protection and can easily get beneath saliva due to lower surface tension Dished-out lesions
62
What lifestyle modifications might be advised for a GORD patient?
Leave at least 2 hours between meals and bedtime Reduce fat, alcohol, coffee, chocolate intake Elevate head during sleep
63
What drugs may cause GORD?
Birth control pill Hormone replacement therapy Ca channel blockers
64
What can be used to treat less severe GORD cases and how?
Antacids/alginic acid Neutralise stomach acid
65
How does alginic acid work?
Detergent which forms a foam 'raft' on top of stomach contents Acts as a physical barrier to reduce reflux
66
Why might gastric motility-stimulation agents be used with a PPI? Why don't we use this?
Increase tone of lower oesophageal sphincter Side effects (Metoclopromide and domperidone)

BMS13 (7 decks)

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