Lecture 11 - GI Flashcards
Where is gastric mucosa secreted from?
mucosal epithelial cells
Why is the gastric mucous layer important?
This mucous layer protects from the cells of the stomach from the acid and enzymes in the lumen of the stomach (otherwise the stomach would eat itself)
What can loss of the mucous layer lead to?
It can allow acid to reach the cells and cause an ulcer
Parietal cells in the stomach make _____ (one of the strong acids known)
HCl
What is the purpose of HCl in the stomach?
This acid is primarily to kill bacteria, viruses and other parasites, not for digestion
What can overproduction of the acid (hyperacidity) lead to?
It can overwhelm the mucous layer and buffer systems and lead to ulcers
What is a systemic antacid?
NaHCO3
NaHCO3 dissociates into?
Na+ and HCO3- (bicarbonate)
What effect does the bicarbonate ion have on the stomach?
The bicarbonate ion isn absorbed into the blood and slightly increases pH (alkalosis)
NaHCO3 is quick, easy, and effective in the ____ term to reduce stomach acid
short
Problems with NaHCO3 antacids?
- Alkalotic urine can increase the deposition of calcium and phosphate to form a kidney stone (cranberry juice does the opposite)
- This increases blood sodium, thus exacerbating HTN
- Acid rebound due to feedback regulation
List some non-systemic antacids
CaCO3
Al(OH)3
Mg(OH)2
Do non-systemic antacids affect extracellular or blood pH?
No
Aluminum and calcium antacids are _______, thus they are often combined with magnesium
constipating
______ ____ receptors in parietal cells stimulate HCl secretion from these cells
Muscarinic Ach
Inhibiton of Muscarinic Ach receptors reduces ____ _______
acid secretion (but not by much)
List an example of a Muscarinic type 1 ACh Receptor blocker
Pirenzipine
*can reduce acid by up to 40%
SE of anticholinergics?
dry mouth, dry eyes, sedation, etc.
Are anticholinergics a good choice?
Not really
-Since they are very non-selective and therefore will cause lots of side effects and limited acid reduction
What are Cytoprotectives?
Drugs which protect cells from acidic damage, either directly or through stimulation of mucous
What are two major Cytoprotective drugs?
- Sucralfate
- Misoprotol
Sucralfate is an ______-based salt
aluminum
Describe Sucralfate
Aluminum base salt:
- Binds to hydrogen ions to form a gooey paste, increasing pH (decreasing acidity)
- Also binds to degenerating cells, forming a protective layer
- “Artificial” mucous
- It is not absorbed into the bloodstream, but can inhibit absorption of other drugs
- Works for 8-12 hours, specifically protects damaged tissue as well as reducing acidity
Describe Misoprostol
Misoprostol is a prostaglandin analogue which stimulates production of the mucosal layer
*Often given with Diclofenac (NSAID) to counteract stomach issues
What does stimulation of H2 receptors in parietal cells cause?
increases HCl production
______ of H2 receptors are highly effective in a number of acid-related disorders
Inhibition
H2 blockers are very _____ to the organ, to the receptor type (do not cross to PGE) and no adverse effect on mucosa
specific
List 3 H2 blockers
- Cimetidine
- Ranitidine
- Famotidine
Cimetidine (H2 blocker):
Causes ____% reduction in acidity
50-60 (moderate)
Cimetidine (H2 blocker):
Binds to Cyt ___ to cause DI
P450
Cimetidine (H2 blocker):
Binds to androgen receptors - so what adverse effects can it cause?
- gynecomastia
- reduced libido
- impotence
Ranitidine (H2 blocker):
Causes _____% reduction in acidity
65-70 (more effective than cimetidine)
Ranitidine (H2 blocker):
Why does it cause less drug interactions than cimetidine?
Only binds P450 at high doses
Ranitidine (H2 blocker):
Does it bind to androgen receptors?
No
**Therefore less side effects
Brand name of Cimetidine?
Tagamet
Brand name of Ranitidine?
Zantac
Brand name of Famotidine?
Pepcid
Famotidine (H2 blocker):
Why is it the most effective?
- Doesn’t bind to P450 at all
- Very few adverse side effects
- Famotidine is the most effective at reducing acid secretion and has the best safety profile
Proton Pump Inhibitors (PPI):
MOA
Inhibit gastric H+/K+ ATPase Proton Pump
Proton Pump Inhibitors (PPI):
Are especially good for ____ reduction of acid
rapid
Proton Pump Inhibitors (PPI):
Where do they bind to?
Bind to H+ extrusion sites and block the release of H+ and Cl-
Proton Pump Inhibitors (PPI):
_____ effective
fairly
Proton pump inhibitors all end in _____
prazole
List some PPI’s
Omeprazole Esomeprazole Lansoprazole Pantoprazole Rabeprazole
PPI’s are especially good for ____
GERD (as well as other acid-dependent disorders)
Proton Pump Inhibitors (PPI):
Are generally ____ and ____
safe and cheap