9.1 - Gastrointestinal Drugs Flashcards
What is an ulcer?
Defined as a rea of erosion passing through the lining of the GI wall
What causes stomach ulcers?
An imbalance between:
Aggressive factors
–> Acid, pepsin (digestive enzyme), bile (irritant), H. Pylori, NSAIDs
and Protective Factors
–> Mucus (protective layer), Pgs, bicarb (buffer), circulation
What is the stomach’s last line of defense against stomach acid?
Sufficient gastric circulation allows epithelial cells to dump acid rather than being damaged by it - this is why chronic stress can predispose someone to stomach ulcers (because blood is shunted from the GI tract)
What fraction of duodenal ulcers are caused by H. Pylori vs NSAIDs?
H. Pylori - 92%
NSAIDS - 5%
What fraction of gastric ulcers is caused by H. Pylori vs NSAIDs?
H. Pylori - 70%
NSAIDs - 25%
What are the two ways NSAIDs cause gastric damage?
Topical
–> gastric epithelial cells are damaged by absorbing an acidic drug (ASA)
Systemic
–> NSAIDs reduce synthesis of Pgs that are protective to gastric mucosa. Less of these protective PGs means less mucus, bicarb, and gastric circulation; as well as an increase in HCl secretion
Increased risks of NSAID related ulcers include:
Pts with a history of ulcer complications, who use multiple NSAIDs and/or high doses, who are on an anticoagulant, or who are 60+ years old.
In what two ways do antacids like magnesium hydroxide, aluminum hydroxide, and calcium carbonate help treat peptic ulcers?
By increasing pH (less acidic environment)
More alkaline environment means reduced activity of pepsin
What adverse effects do all antacids share?
They may reduce the absorption of certain drugs, such as digoxin, tetracycline, or ciprofloxacin
What are the five kinds of drugs used to treat peptic ulcers?
- Antacids
- Mucosal defenses
- H2 Antagonists
- PPIs
- Antibacterial drugs
What two drugs form a protective barrier over gastric mucosa?
Sucralfate and Bismuth Subsalicylate
What is an adverse effect of sucralfate?
Constipation
On top of forming a protective barrier over gastric mucosa, what does bismuth subsalicylate do for ulcers?
It also have bacteriostatic, antisecretory, and anti-inflammatory activities
What are the adverse effects of bismuth subsalicylate?
Can cause black tongue and feces
What kind of drug is misoprostol? What is its mechanism of action?
A PGE1 analogue
–> Synthetic PG stimulates submucosa blood flow, and increased production of bicarb and mucus
–> Also attenuates histamine-induced gastric acid secretion