Acid Peptic Disorders Flashcards
H. pylori ulcers
- Location: Duodenum > stomach
- Epigastric pain
- Superficial ulcer
- Less severe GI bleeding
NSAID ulcers
- Location: Stomach>duodenum
- asymptomatic
- Deep ulcer
- More severe GI bleeding
Stress ulcer
- ACUTE!
- Location: Stomach>duodenum
- Asymptomatic
- Superficial ulcer
- More severe GI bleeding
Parietal cells contain receptors for what 3 things?
- Gastrin (CCK-B)
- from G cells - Histamine (H2)
- Acetylcholine (muscarinic, M3)
How do antacids work
weak bases that react with stomach acid to form a salt and water
How long do antacids typically work?
If taken 1 hour after a meal, they effectively neutralize gastric acid for up to 2 hours
Antacids: Sodium Bicarbonate
Ex. baking soda, alka Seltzer
-React with gastric acid to form carbon dioxide and sodium chloride
ADE: 1. gastric distension 2. belching**
- be careful if kidneys don’t work, could cause metabolic alkalosis
- becareful with NaCl absorption and fluid retention
Antacids: Calcium carbonate
Ex. Tums, Os-cal
-Reacts more slowly to form CO2 and CaCl2 (calcium chloride)
ADE: 1. belching 2. metabolic alkalosis 3. milk-alkali syndrome –>hypercalcemia if taken with dairy
Antacids: Magnesium hydroxide and aluminum hydroxide
Maalox (contains both magnesium and aluminum)
MOA:: reacts slowly to form magnesium chloride
- No gas or belching :)
- metabolic alkalosis uncommon
ADE: unabsorbed magnesium salts may cause diarrhea. Aluminum salts may cause constipation
Because antacids interact and effect the absorption of some medications, which should not be given within 2 hours of antacids?
- Tetracyclines
- Fluroquinolones
- Itraconazole
- Iron
H2 Receptor Antagonists
Ex. Cimetidine, Ranitidine, Famotidine, Nizatidine
-1st pass hepatic metabolism** (except Nizatidine)
Metabolism: hepatic, glomerular filtration, renal tubular secretion
When should H2 receptor blockers be given?
Bedtime
Most potent and least potent H2 blockers?
Least potent: cimetidine
Most potent: Famotidine
How long do H2 blockers work for?
10 hours (prescription strength)
6 hours (OTC)
What is the biggest ADE of H2 blockers?
Possible risk of nosocomial PNA in critically ill patients
Cimetidine unique ADEs
- Cytochrom P450 metabolized
- inhibits dihydrotestosterone to androgen receptors
- increases serum prolactin levels (galactorrhea in women)
- gynecomastia/impotence in men
PPIs: pharmacokinetics
Bioavailability is decreased by about 50% by food
- Irreversible inactivation of proton pump (H+/K+ ATPase which only exists in stomach)
- Rapid first-pass systemic hepatic
- Take 30-60 minutes before eating*
- Take at breakfast*
PPI: ADEs
- Diarrhea*
- Potentially effects absorption of iron, calcium, magnesium (increased fracture risk)
- increased risk of C. diff infection
- Rebound acid hypersecretion
PPIs: Drug interactions
- Omeprazole may inhibit metabolism of Warfarin
- Pantoprazole = no significant drug interactions
- Clopidogrel is a prodrug and can have reduced activation if used with some PPIs
What chemical is important in stimulating mucus and bicarbonate secretion and mucosal blood flow?
prostaglandins
Mucosal Protective Agents: Sucralfate
- forms physical barrier that restricts caustic damage
- Stimulates mucosal prostaglandin and bicarbonate secretion
Sucralfate: ADE
Constipation* (due to aluminum salt)
-Can bind to other medications and impair absorption
Gastrointestinal mucosa synthesize which prostaglandins?
PGE
PGF
Misoprostol
- PGE1
- Short half-life, so take it 3-4 times a day
MOA: inhibit acid, protect mucosa
other: stimulate intestinal electrolyte and fluid secretion, intestinal motility, uterine contractions
Misoprostol: ADE
- Diarrhea
- Cramping abdominal pain
- DO NOT USE in pregnancy or in women with child bearing potential (unless negative hCG), and on contraception)
Bismuth Compounds: types
- Bismuth subsalicylate (ex. Pepto-Bismol)
- OTC - Bismuth subcitrate potassium
- Rx
- Contains metronidazole and tetracycline for treating H. pylori
Bismuth Compounds: metabolism
- 99% of bismuth ends up in stool
- Salicylate dissociates with bismuth in the stomach and is readily absorbed and excreted in the urine.
Bismuth compounds: pharmacodynamics
Bismuth: creates a protective layer against pepsin and acid
-Bismuth has direct antimicrobial effects —>binds enterotoxins (antimicrobial activity against H. pylori)
Bismuth subsalicylate: reduces stool frequency and liquidity (inhibits intestinal prostaglandins and chloride secretion)
Bismuth Compounds: ADE
- blackening of stool
- darkening of tongue
- AVOID in renal insufficiency –> bismuth toxicity with encephalopathy, ataxia, headaches, confusion
-Remember that salicylate toxicity can cause tinnitus!
H. Pylori: Triple therapy Tx
PPI + Clarithromycin + Amoxicillin/Metronidazole
for 14 days
H. Pylori: Bismuth quadruple therapy
PPI + Bismuth + metronidazole + tetracycline
