Gastric ulcers and duodenal ulcers Flashcards
What are the three protective mechanisms of the lining of the stomach?
Bicarbonate ions
Mucous secretions
Prostaglandins stimulating mucous and bicarbonate production
What are the two factors needed to make food into chyme?
Acid secretions from the parietal cells of oxyntic glands
Pepsinogens from chief cells
When does pain present in duodenal ulcers?
After mealtimes
Relieved when having a meal as the pyloric sphincter closes
What are the factors that could cause damage to the GI mucosa?
Increased acid secretion/decreased bicarbonate secretion Decreased thickness of mucosal layer Increase in pepsin 1 Reduced mucosal blood flow Helicobacter pylori
What is known as the ‘triple therapy’?
Antibiotics (treat H. pylori)
Drugs which reduce gastric acid secretions
Cytoprotective drugs (promotes healing of ulcers)
How is the presence of Helicobacter pylori detected?
Patient is given urea with a radioactive carbon isotope. The detection of the isotope-labelled carbon dioxide in the breath indicates the presence of urease (used by the bacteria to metabolise urea).
What stimulates gastric acid secretion?
Thinking about food: vagal stimulation
Food: drop in pH in Antrum area causes gastrin secretion -> CCK on parietal cells
Chemicals: amino acids causes gastrin release which stimulates histamine release
What inhibits gastrin?
Somatostatin produced by D cells
Secretin
Gastrin inhibitory peptide
What are the types of drugs used to treat gastric acid secretion?
Proton pump inhibitors
Histamine (H2) receptor antagonists
Anti-muscarinics
Name a proton pump inhibitor and its action
Omeprazole
Inhibits H+/K+ ATPase pump
How is the chosen proton pump inhibitor selective for those in the stomach?
It is a weak base so it accumulates in the cannaliculi of parietal cells and concentrates its action for 2-3days, minimising its effect on other ion pumps in the body.
When would you use proton pump inhibitors?
Peptic ulcers resistant to histamine antagonists
Oesophagitis
GERD
Prophylaxis of peptic ulcers in ICU and those taking NSAIDs, aspirin, anticoagulant and anti platelets
Name some histamine receptor antagonists and its MOA
Ranitidine, Cimetidine
Competitive antagonism of H2 receptor
Name cytoprotective drugs
Sulcrafate
Bismuth chelate
Misoprostol
What is the MOA of sulcrafate?
Takes a strong neg. charge in acidic environment and therefore binds to large positive molecules e.g. proteins, glycolproteins. This then makes gel-like complexes which protects the ulcers and limits H+ diffusion and pepsin degradation of mucus.
Stimulates prostaglandins to make bicarbonate, mucous and stop h. pylori
