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(Drugs Used in the Treatment of Gastrointestinal Diseases) - Coggle Diagram

- - - - Secrete up to 2L acid/day
      - Optimal pH for pepsin: 1.8–3.5
    - - Exchanges H+ for K+
      - Stimulated by ACh, histamine, gastrin
    - - Released when pH < 3
      - Inhibits parietal cells + histamine/gastrin release
    - - Cephalic: ACh from thought/smell of food
      - Gastric: Food stretch → gastrin release
      - Intestinal: Chyme triggers negative feedback
  - - - H. pylori (most common)
      - NSAIDs, alcohol, stress, smoking
    - - Tumor → excess gastrin → ulcers + diarrhea
    - - Burning pain, bloating, nausea
      - Severe: black stool, vomiting blood, weight loss
    - - GI bleeding
      - Perforation
      - Cancer (H. pylori-related)
  - - - • Types
        
        Aluminum hydroxide (constipation)
        
        Magnesium hydroxide (diarrhea)
        
        Calcium carbonate (acid rebound)
        
        Sodium bicarbonate (metabolic alkalosis risk)
      - • Combination Products
        
        Balanced AE profile
        
        Minimize aluminum absorption
      - • Adverse Effects
        
        Constipation/diarrhea
        
        Metabolic alkalosis
        
        Renal insufficiency contraindicated
    - - • Examples
        
        Cimetidine, Ranitidine, Famotidine, Nizatidine
      - • Mechanism
        
        Block histamine → ↓ cAMP → ↓ acid
      - • Uses
        
        GERD, stress gastritis (IV), mild peptic ulcer
      - • Adverse Effects
        
        Headache, fatigue, CNS effects (IV cimetidine)
        
        Endocrine effects (↑ prolactin, ↓ estradiol)
      - • Drug Interactions
        
        Cimetidine inhibits CYP enzymes
    - - • Examples
        
        Omeprazole, Esomeprazole, Lansoprazole, Pantoprazole, Rabeprazole
      - • Mechanism
        
        Irreversible inhibition of H⁺/K⁺ ATPase
      - • Uses
        
        GERD (first-line), peptic ulcer, Zollinger-Ellison, GI bleed prophylaxis
      - • Adverse Effects
        
        Headache, abdominal pain, B12 deficiency
        
        ↑ infection risk, ↑ gastrin, ECL cell hyperplasia
      - • Drug Interactions
        
        ↓ absorption of digoxin, ketoconazole
    - - • Sucralfate
        
        Forms protective layer over ulcers
        
        Use: Peptic ulcer, stress gastritis
        
        AE: Constipation, aluminum toxicity (renal failure)
    - - • Triple Therapy
        
        PPI + Clarithromycin + Amoxicillin / Metronidazole
      - • Quadruple Therapy
        
        PPI + Bismuth subsalicylate + Metronidazole + Tetracycline
      - • Side Effects
        
        GI upset, metallic taste
        
        Risk of antibiotic resistance
    - - • Bulk-forming
        
        Psyllium, methylcellulose
        
        AE: Bloating, flatulence
      - • Osmotic
        
        Polyethylene glycol, lactulose, Mg salts
        
        AE: Dehydration, electrolyte imbalance
      - • Stimulant
        
        Senna, cascara
        
        AE: Dependency, melanosis coli
      - • Stool Softeners
        
        Docusate
        
        AE: Minimal; safe long-term
    - - • Opioid Agonists
        
        Loperamide, diphenoxylate
        
        MOA: Decrease motility, increase water absorption
        
        AE: Constipation, CNS effects (diphenoxylate)
      - • Adsorbents
        
        Kaolin-pectin, bismuth subsalicylate
        
        AE: Salicylate toxicity (bismuth in large doses)
      - • Somatostatin Analogs
        
        Octreotide
        
        MOA: Inhibits secretions and motility
        
        Use: Secretory diarrhea (carcinoid, AIDS, dumping syndrome)
        
        AE: Gallstones, glucose intolerance
    - - • 5-HT₄ Agonists
        
        Tegaserod
        
        MOA: Enhances Ach & CGRP release → ↑ motility
        
        Use: Chronic constipation, IBS-C
        
        AE: Diarrhea, expensive
      - • 5-HT₃ Antagonists
        
        Alosetron
        
        MOA: Blocks sensory signals in gut → ↓ visceral pain
        
        Use: IBS-D (female-predominant)
        
        AE: Ischemic colitis (black box warning), severe constipation
    - - • 5-HT₃ Antagonists
        
        Ondansetron, Granisetron
        
        Use: chemo/radiotherapy-induced nausea, post-op
        
        AE: Headache, constipation
      - • NK₁ Antagonists
        
        Aprepitant
        
        Use: Delayed emesis
        
        AE: Fatigue, hiccups
      - • Dopamine Antagonists
        
        Prochlorperazine, Promethazine
        
        Use: Motion sickness, chemotherapy
        
        AE: Extrapyramidal symptoms, sedation
    - - • Metronidazole
        
        Use: Amebiasis, Giardiasis, Trichomoniasis
        
        AE: Metallic taste, headache
      - • Tinidazole
        
        Similar to metronidazole but better tolerated
      - • Chloroquine
        
        Use: Intestinal amebiasis (luminal)
    - - • Mebendazole
        
        Broad-spectrum; inhibits microtubules
      - • Niclosamide
        
        Interferes with energy metabolism
      - • Praziquantel
        
        Increases Ca²⁺ permeability → spastic paralysis
        
        Use: Flukes, schistosomes
        
        AE: Dizziness, headache
    - - • Ganciclovir / Foscarnet
        
        Use: CMV gastroenteritis (immunocompromised)
        
        AE: Bone marrow suppression, renal toxicity
      - • Acyclovir
        
        Use: HSV esophagitis
        
        AE: Nephrotoxicity
    - - • Rotavirus
        
        Vaccine available, affects infants
      - • Norovirus
        
        Highly contagious, outbreaks
      - • Adenovirus
        
        Affects infants and immunocompromised
      - • CMV
        
        Severe in neonates and immunosuppressed
      - • HSV
        
        Can cause esophagitis in immunosuppressed
  - - - Cimetidine inhibits CYP enzymes
      - PPIs affect absorption of digoxin, ketoconazole
    - - Vitamin B12 deficiency (PPIs)
      - Long-term ↑ gastrin levels (PPIs)
      - Neurological side effects (Metronidazole, Cimetidine)
    - - Lifestyle changes before laxatives
      - Avoid alcohol with Metronidazole
      - Take PPIs on empty stomach