23. Drugs Affecting Acid Secretion Flashcards
What are the defensive factors of the gastric mucosa?
Epithelial integrity, cell replication and restitution, mucous membrane barrier, vascular supply.
What are the aggressive factors of the gastric mucosa?
Acid, helicobacter pylori, drugs.
What are the targets for drugs to act on the parietal cell?
Stimulatory receptors of the baso-lateral membrane, and the proton pump.
What are the receptors on the baso-lateral membrane of the parietal cell?
Acetylcholine, cholecystokinine B (CCK-B), histamine 2 receptors.
What is the receptor of the apical membrane of the parietal cell?
HK ATPase exchanger - the proton pump.
What is the main target for drugs in peptic disorders?
Proton pump.
What is the action of PPI?
Blocks the HKATPase on apical membrane of parietal cells. The pump has to be active for it to work on it.
When do PPIs have maximum efficacy?
After 2-3 days.
Why do patients normally feel immediately better having taken H2 receptor antagonists?
Because they have a short half life so act quickly.
What is the dosing of H2 receptor antagonists?
Twice daily.
What are the neuroendocrine regulators that act on parietal cells?
Cholecystokinine B, histamine, dopamine, gastrin.
What percentage of duodenal ulcer cases have H. pylori infection?
96%.
What percentage of gastric ulcer cases have H. pylori infection?
75%.
What is the step up ladder used in drugs for peptic disorders?
Anatacids -> alginates -> H2 receptor antagonists -> PPIs.
What are the issues with using the H2RA cimetidine?
ADRs: gynaechomastia in men. DDIs: inhibits CYP450 metabolism.