Drugs to treat disorder of gastric acid secretion Flashcards Preview

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Flashcards in Drugs to treat disorder of gastric acid secretion Deck (13)
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1

What is an antacid?

An antacid is any substance, generally a base, which counteracts stomach acidity. ​

They act by buffering gastric acid, thereby raising the gastric pH.

e.g.: Aluminum hydroxide and magnesium hydroxide (Maalox®) ​
Calcium carbonate and magnesium carbonate (Rennie®) ​

2

What is an alginate?

​Anionic polysaccharides that form a viscous gel upon binding water.​

Often combined with antacids for use in reflux oesophagitis.​

Increase the viscosity of stomach contents and can protect the oesophageal mucosa from acid reflux. ​

The viscous gel (‘raft’) floats on the surface of the stomach contents, thereby reducing symptoms of reflux.

e.g. sodium alginate, sodium bicarbonate, calcium carbonate Gaviscon®​

3

What are histamine H2-receptor antagonists?

Competitively inhibit histamine actions at H2-receptors. ​

​Decrease basal and stimulated acid secretion.​

e.g. ranitidine Zantac®​

4

What do proton pump inhibitors do?

Irreversibly inhibit the H+/K+-ATPase pump, the terminal step in the acid secretory pathway.

Decrease both basal and stimulated acid secretion.​

Are more effective than H2-receptor antagonists.​

Are inactive at neutral pH. ​

Accumulate in secretory canaliculi of parietal cells and are activated in acid environment. therefore very specific.

e.g. Omeprazole Losec®, Prilosec®, Zegerid®​

Lansoprazole Prevacid®, Zoton®, Inhibitol® ​

5

What are the conditions requiring drug treatment of acid secretion?

1) reflux oesophagitis​
2) peptic ulcer​
- non-steroidal anti-inflammatory drugs (NSAIDS)​
- Zollinger-Ellison Syndrome​
- H. Pylori infection

6

What are the symptoms and complications of reflux oesophagits?

Symptoms​:
Heartburn​
Regurgitation​
Haematemesis – vomiting of blood caused by irritation of gastric lining​

Complications​:
Oesophageal ulceration​
Peptic stricture – in elderly, narrowing of oesophagus​
Barrett’s oesophagus

7

How do prostaglandins renew the gastric mucosal barrier?

Prostaglandins E2 and I2 simulate and support renewal of the gastric mucosal barrier by:​
1) stimulating gastric mucus production​
2) stimulating bicarbonate secretion​
3) inhibiting gastric acid production​
4) promoting local healing

8

What is Zollinger-Ellison syndrome?

Increased levels of the gastrin are produced. (Gastrin causes parietal cells to secrete HCl)​

Often, the cause is a gastrin-producing tumour (gastrinoma) of the duodenum or pancreas. Ectopic tumour. ​

Gastrin increases acid secretion, which can lead to peptic ulcers (95% of patients).​

Gastrin also acts as a trophic factor for parietal cells, causing parietal cell hyperplasia. ​

Therefore there is an increase in the number of acid secreting cells, with each producing acid at a higher rate.

9

What is the treatment for Zollinger-Ellison syndrome?

Proton pump inhibitors and H2-receptor antagonists are used to slow down acid secretion.​

Tumours are removed surgically (if possible) or treated with chemotherapy.

10

What does Helicobacter Pylori do?

A spiral-shaped Gram-negative bacterium, which damages stomach and duodenal tissue.​

Produces and secretes urease, which breaks down urea into CO2 and NH3.​

NH3 neutralises gastric acid.​

H. pylori penetrates mucus barrier, facilitating acid penetration.​

NH3, other bacterial products, and acid damage epithelial cells.

11

What is the treatment for H. pylori infection?

Eradication regimens include antibiotics (to get rid of H Pylori) and a proton pump inhibitor (to suppress acid secretion to make H pylori less effective at damaging mucosal membrane).​

Eradication of H. pylori can produce long-term remission of ulcers.

12

What are the causes of under-secretion of gastric acid?

Achlorhydria (absence of gastric acid)/ Hypochlorhydria (reduction of gastric acid): absence / deficiency of hydrochloric acid in gastric juice, e.g. ​
- iatrogenic​
- atrophy of gastric mucosa (older adults)

13

What are the consequences of under-secretion of gastric acid?

impaired ability to digest and absorb certain nutrients, such as iron, and the B vitamins. ​

increased vulnerability of GI tract to bacterial infection.