GIT - Drugs used for Acid-Peptic Diseases Flashcards Preview

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Flashcards in GIT - Drugs used for Acid-Peptic Diseases Deck (20):

Classes of drugs used for acid-peptic diseases & examples

Agents that reduce intra-gastric acidity
1. Antacids (NaHCO3, CaCO3, Mg(OH)2, Al(OH)3)
2. H2 Receptor Antagonists - H2 Blockers (Ranitidine, Famotidine)
3. Proton Pump Inhibitor (Omeprazole)

Mucosal Protective Agents
1. Sucralfate (salt of sucrose complexed to sulfate Al(OH)3)
2. Bismuth Compounds (Bismuth subsalicylate, Bismuth subcitrate potassium)
3. Synthetic PGE1 analog (Misoprostol)

Treatment for H. pylori eradication


Mechanism of action of antacids

Neutralize gastric acid to form salt & H2O - decreases gastric acidity but does not prevent gastric acid production

Rate of neutralization: NaHCO3 > CaCO3 > Mg(OH)2 > Al(OH)3


Uses of antacids

Non-prescription remedy for heartburn & dyspepsia


Toxicity of antacids (6)

1. Na - Fluid retention, CHF, HTN
2. Ca - Hypercalcemia, rebound acid secretion
3. HCO3, CO3 - CO2 gas formation - gastric distension, belching
4. Metabolic Alkalosis, Milk-alkali Syndrome
5. Mg - Osmotic diarrhea
6. Al - Constipation
Mg & Al - combined formulation to minimize impact on bowel function


Contraindications of antacids (2)

1. Patients with renal insufficiency
2. Affects absorption of other medications - do not give within 2h of other drugs


Mechanism of action of H2 blockers

Competitive inhibition of H2 receptors on parietal cells - suppresses gastric acid secretion & pepsin concentration induced by histamine, gastrin and acetylcholine


Uses of H2 blockers (2)

1. Nocturnal acid secretion (due to histamine) - very effective
2. Meal-induced acid secretion (gastrin & ACh) - modest effect


Toxicity of H2 blockers (3)

1. Mental Confusion - in critically ill patients/in renal/hepatic dysfunction
2. Anti-androgenic, inhibits estradiol metab, increases serum prolactin - gynecomastia, impotence, galactorrhea
3. Inhibits cytochrome P450 - prolongs half life of other drugs eg warfarin, theophylline


Mechanism of action of PPI

1. Inhibits H/K ATPase in parietal cells - most potent gastric acid secretion inhibitor
- forms covalent disulphide bond, inhibits active pumps for their entire lifespan, takes 3-4 days to fully inhibit acid secretion
2. Has some anti-microbial activity against H. pylori


Toxicity of PPI

Generally safe
- Headache, nausea, constipation, flatulence, diarrhea

Unproven safety concerns
- Vit B12 deficiency, Fe & Ca deficiency & risk of osteoporosis, enteric Clostridium difficile infection, pneumonia, gastric cancer


Mechanism of action of sucralfate

1. Negatively charged sucrose sulfate binds to positively charged proteins at ulcer crater - forms a viscous, tenacious gel that prevents further acid attack
2. Stimulates mucosal prostaglandin (mainly PGE2) & bicarbonate secretion


Uses of sucralfate

1. Prevents stress-related bleeding in critically ill patients


Toxicity of sucralfate (2)

1. Constipation (due to Al salt)
2. Impairs absorption of other drugs (large molecule)


Mechanism of action of bismuth compounds

1. Forms a protective layer coating ulcer beds against acid & pepsin
2. Stimulates prostaglandin, mucus & bicarbonate secretion
3. Direct anti-microbial activity against H. pylori


Uses of bismuth compounds (3)

Bismuth subsalicylate (OTC)
1. Dyspepsia
2. Acute diarrhea, Traveler's diarrhea (anti-microbial effects binds enterotoxins)

Bismuth subcitrate potassium
3. Quadruple therapy for eradication of H, pylori


Toxicity of bismuth compounds

Excellent safety profiles
1. Harmless blackening of stool & darkening of tongue (reversible)


Mechanism of action of misoprostol

Binds to GPCR PGE2 receptors
- Low dose (cytoprotective) - promotes HCO3 & mucus secretion, enhances mucosal blood flow
- High dose (anti-secretory) - inhibits gastric acid secretion


Uses of misoprostol

1. Prevent NSAID induced peptic ulcers


Toxicity of misoprostol (5)

1. Abdominal pain
2. Diarrhea
3. Abortion (uterine contraction)
4. Bone pain
5. Hyperostosis

Limited use due to adverse effect profile, multiple daily dosing (non-compliance) & development of COX-2 selective NSAIDs


H. pylori eradication

Triple Therapy
- 2 antibiotics (ampicillin + metronidazole/clarithromycin) + 1 PPI for 7-14 days, continue PPI after for 4-6 weeks to ensure complete ulcer healing
- PPI (A) Direct anti-microbial properties (B) Raises intragastric pH, lowers MIC of antibiotics against H. pylori

Quadruple Therapy
- 2 antibiotics + 1 PPI + Bismuth
- Bismuth - Direct antimicrobial activity against H. pylori

Common side effects: Diarrhea, nausea, vomiting