Week 5 Upper Gastrointestinal Disorders Flashcards
. List and explain the 4 defensive factors which protect the stomach and duodenum from self-digestion.
Mucus – forms a barrier to protect underlying cells from gastric acid and pepsin.
Bicarbonate – neutralizes any acid which penetrates the mucus.
Blood flow – maintains integrity or health of the mucosa
Prostaglandins – Stimulates mucus and bicarbonate, vasodilates blood vessels, suppresses gastric secretion
List and explain 5 aggressive factors which predispose the stomach and duodenum to ulcerations.
Helicobacter pylori (H. pylori) – gram-negative bacillus which lives between the mucus layer and the mucosa. Produces CO2 and ammonia from urea which damages the mucosa.
NSAIDs – decreases the production of prostaglandins which decreases blood flow, decreases bicarbonate and mucus secretion, and increases gastric acid.
Gastric Acid – injures cells of the mucosa and activates pepsin.
Pepsin – breaks down protein of the gut wall.
Smoking – delays healing of ulcers and increases risk of recurrence.
What are three mechanisms of action for antacids?
Binds gastric acid and forms a neutral salt, inactivates pepsin if pH > 5, and stimulates prostaglandins.
How are antacids administered in relation to meals, sleep, or other drugs? If not eating, how often are they given?
1 and 3 hrs after meals and at bedtime, 1 hour before another drug, or every 2 hours if not eating
Which antacids can cause complications in heart failure and renal disease?
Aluminum hydroxide and sodium bicarbonate – heart failure, magnesium hydroxide – CNS toxicity in renal patients
How do histamine2 receptor antagonists work?
Block H2 receptors on parietal cells which suppress gastric acid secretion and decrease the hydrogen ion concentration in gastric acid.
How are histamine2 receptor antagonists administered in relation to meals?
May be taken without regard to meals, except take Tagamet with food
Which histamine2 receptor antagonist is noted for drug-drug interactions caused by inhibition of hepatic drug-metabolizing enzymes?
cimetidine (Tagamet)
Which histamine2 receptor antagonist is known for its ability to block androgen effects?
cimetidine (Tagamet)
Proton-pump inhibitors may decrease the absorption of antifungals by what action?
Decreased gastric acid production
Proton pump inhibitors are usually given when?
Usually given before the first large meal of the day. Some may be given at any time.
How long does it take for full recovery of the H+, K+-ATPase pump after stopping a proton pump inhibitor?
Why? How long for partial recovery?
Weeks due to irreversible inhibition. 3-5 days.
Why is misoprostol (Cytotec) used?
What are the mechanisms of action?
Prevention of NSAID-caused gastric ulcers. Stimulates the secretion of mucus and bicarbonate, vasodilates blood vessels, suppress gastric acid secretion. Replaces prostaglandins.
Why is misoprostol (Cytotec) not given during pregnancy?
Stimulates uterine contractions.
How does sucralfate (Carafate) work? When should it be given?
Polymerization and cross-linking occurs when the pH is < 4. It adheres to the crater for 6 hours. Given on an empty stomach.
