G.I. Flashcards
Peptic Ulcer Disease
10-15% of people
Can occur anywhere in the upper GI exposed to stomach acid and pepsin.
Occurs when corrosive action of gastric acid overcomes the protection of mucous.
Helicobacter Pylori and overuse of NSAIDs.
Acid Production
Proton from dissociated carbonic anhydrase is pumped from the parietal cell to the lumen of the stomach. Chloride ion follows producing HCL.
Control of Acid Secretion
Gastrin produced on the duodenum and stomach stimulating acid secretion by stimulating receptors on parietal cells.
Parasympathetic nerves increases acid production.
Histamine produced near the parietal cells and promote acid production. Histamine is required for the other two mechanisms.
H2 histamine receptor.
Mucosal Defense
Mucous secreted by goblet cells
Made up of glycoproteins, water and electrolytes.
Protects from acid and pepsin
Prostaglandins inhibits acid secretion and stimulates mucous production.
Can be inhibited by chemotherapy and extreme stress
H. Pylori
Can cause spontaneous ulcers
Antimicrobials are curative
Weakens mucous defense mechanism
Found using endoscopy
Rationale For Therapy
Neutralize Acid (antacids)
Inhibit Secretion
- H2 antagonists
-Proton pump inhibitors
Enhance Defense
-Sucralfate
-Misoprostol
Eradicate H. Pylori
-Antimicrobials.
Sodium Bicarbonate
Alka Seltzer
HCl + NaHCO3 -> NaCl + H2O + CO2
Possible distension and metabolic alkalosis
Rapid onset
High sodium content
Adequate for occasional relief but not long term treatment
Calcium Carbonate
Tums
CaCO3 + 2HCl -> CaCl2 + H2O + CO2
Can cause systemic alkalosis. Less Distension
High Ca intake or poor renal function can cause “milk alkali” including hypercalcemia, kidney stones, and renal damage
Acid rebound
Occasional management
Can decrease bioavailability or glycosides, tetracyclines, and phenytoin.
Magnesium Hydroxide
Mg(OH2) + 2HCL -> MgCl2 + 2H2O
Rarely causes alkalosis with magnesium remaining in the lumen
Diarrhea is a common side effect, so coadminister with something with a constipating effect
Aluminum Hydroxide
Very much the same as Magnesium Hydroxide, except cause constipation due to astringent effect
Reduces absorption of phosphate causing hypophosphatemia.
Possible development of Alzheimer’s
Maalox
Magnesium + Aluminum
Use of Neutralizing Agents
Symptomatic relief and act quickly
Not primary for PUD
Many contain significant sodium
Can affect drug dissolution in the stomach and delay gastric emptying.
Na and Ca can raise urinary pH and alter excretion of drugs
H2 Antagonists
Cimetidine
- Inhibits CYP450 so drug interactions
-Can have anti androgen effect causing gyno
Famotidine
Nizatidine
Reduce acid secreted in response to histamine.
Used for both acute treatment and prevention of relapse
Zollinger Ellison Syndrome and Reflux -esophagitis
Doesn’t interact with other histamine receptors
Proton Pump Inhibitors
-azole
Very effective at reducing acid secretion and have some effect on H. Pylori as well
Inactive prodrugs converted to active form in the parietal cell canniculus. Inactivates H+/K+ ATPase irreversibly.
Effective at treating many acid related conditions
Potential for drug interactions
AE: Possible microbial overgrowth of the upper GI and carcinoid tumors of the stomach.
Osteopenia in women and possible vitamin B12 deficiency
Interaction with Clopidogrel, particularly with Omeprazole and Esomeprazole. Pantoprazole has the least effect. Clopidogrel requires activation by CYP2C19.
Sucralfate
Enhance Mucous defense
Polymerizes and forms a coating that binds to proteins in the ulcer.
Should be taken before meals
AE: Constipation
Al is present, so can decrease effectiveness of glycosides and other meds and effect renal function.
