Block 15 Flashcards
(20 cards)
Mechanism of Ranitidine
Histamine (H2) Receptor antagonist
- selectively, reversibly and competitively block H2 histamine receptors on parietal cells membranes
- inhibits basal + stimulated gastric acid secretion
Which type of drugs can be used for acute relief of heartburn symptoms?
Histamine (H2) receptor antagonists –> more rapid onset of action than PPIs
Mechanism of PPI (proton pump inhibitors)
bind covalently and irreversibly to inhibit H+/K+-ATPase in gastric parietal cell
reduces basal + stimulated acid secretion
How are PPIs are administered?
PPIs are administered as inactive prodrugs + accumulate in canaliculus of parietal cells before being protonated + converted to active form
What are antacids?
weak bases that buffer or neutralise gastric HCL to form a salt + water, reducing gastric acidity
Give 2 examples of systemic antacids
- Sodium bicarbonate
- Calcium carbonate
Sucralfate
mucosal protective agent
provides a physical barrier over the surface of a gastric ulcer + enhances the gastric mucosal protective system
Misoprostol
synthetic prostaglandin E1 analogue
helps create alkaline mucus layer + inhibits gastric acid secretion
Give an example of an Adsorbent and how it acts
Bismuth subsalicylate
- absorbs bacterial toxins + fluid in the gut
Loperamide MoA
non-selective Ca2+ channel blocker AND binds to opioid muRs in myenteric plexus of lrg intestine
==> SLOWS intestinal motility
Give 2 examples of antispasmodics
Mebeverine
Scopolamine - competitive antagonist at muscarinic Rs
Which agents help to rebalance fluid + electrolytes lost during a diarrhoeal episode?
Oral rehydration agents
Give an example of an NK1 antagonist
Aprepitant
Aprepitant MoA
NK1Antagonist
- blocks action of neurokinin-1 (substance p) in the brain
Diphenhydramine MoA
block vestibular system input into chemoreceptor trigger zone
MoA of Dopamine antagonists
block D2 dopamine receptors in medullary chemoreceptor trigger zone prevent vomiting e.g. Metoclopramide
Ondansetron MoA
serotonin R antagonist:
block 5-HT3 receptors in the CNS and GI tract.
Activation of these receptors normally triggers vomiting
Bulk forming laxatives
- improve stool formation by adding bulk to the diet
- are insoluble + nonabsorable from the intestine
- absorb + retain water which softens + hydrates faecal material
Give an example of a faecal softener and explain how they act
Example: Docusate
softens stools by decreasing surface tension + increasing water/intestinal fluid penetration into stools
MoA of Osmotic Laxatives
- increase water in the large intestine to soften the stool and promote bowel movement
- stretching of bowel lumen due to increased water stimulates peristalsis
Examples: Magneisum Hydroxide
