349.3 🏥 內科專科考前版

349.3.1 Mechanistic Deep Dive

349.3.1.1 H. pylori Pathogenesis

  • Survives in gastric acid (urease produces NH3)
  • Adheres via BabA, SabA
  • Damages mucosa
  • VacA, CagA virulence factors
  • Triggers chronic inflammation → ulcer or atrophy + cancer

349.3.1.2 NSAID Mechanism

  • COX-1 inhibition → ↓ prostaglandins → ↓ mucosal protection
  • COX-2 selective less ulcerogenic
  • Higher doses + longer duration → more ulcerogenic

349.3.1.3 Vonoprazan Mechanism

  • Potassium-competitive acid blocker (PCAB)
  • Faster onset + more sustained acid suppression
  • Effective when PPI fails
  • Especially helpful for severe acid suppression needs

349.3.2 Recent Trials & Updates

349.3.2.1 Vonoprazan FDA 2022

  • For H. pylori
  • Higher eradication rates
  • Less affected by CYP2C19 polymorphisms

349.3.2.2 Levofloxacin Resistance

  • Increasing globally
  • Use for rescue when standard fails

349.3.2.3 Pylera (Combined Bismuth-Based)

  • Convenient quadruple therapy

349.3.2.4 CYP2C19 Polymorphisms + PPI

  • Poor metabolizers have higher PPI levels
  • Extensive metabolizers may have reduced efficacy
  • Asian populations: higher poor metabolizer prevalence

349.3.3 High-Yield Specialist Points

349.3.3.1 PPI Side Effects (Long-Term)

  • B12 deficiency
  • Hypomagnesemia
  • C. diff (3-4x risk)
  • Pneumonia (mild ↑)
  • Hip fracture (controversial)
  • Gastric polyps
  • Iron deficiency

349.3.3.2 H2 Receptor Antagonists

  • Famotidine preferred (ranitidine recalled)
  • Less potent than PPI
  • Tachyphylaxis chronic use

349.3.3.3 Antacids

  • Calcium, magnesium, aluminum
  • Quick relief, short duration

349.3.3.4 Sucralfate

  • Mucosal protectant
  • Limited use now (interferes with absorption)

349.3.3.5 Misoprostol

  • PG analog
  • For NSAID-induced; less used (diarrhea, abortifacient)

349.3.3.6 Bismuth Subsalicylate Side Effects

  • Black stool, black tongue
  • Salicylate concerns
  • Rare encephalopathy

349.3.3.7 Antibiotic Resistance Patterns

  • Clarithromycin: 20-30%+ globally
  • Metronidazole: 30-40%+
  • Levofloxacin: 20%+
  • Amoxicillin + tetracycline: < 5%

349.3.3.8 Penicillin Allergy Alternatives

  • Quadruple therapy (no amoxicillin needed)
  • Levofloxacin-based

349.3.3.9 Pediatric PUD

  • Less H. pylori (mostly idiopathic or stress)
  • Adolescent rates similar to adult
  • Diagnosis + treatment similar

349.3.3.10 Pregnancy + H. pylori

  • Generally defer treatment
  • If needed: amoxicillin + clarithromycin (not first-trimester)
  • Quadruple usually avoided

349.3.3.11 Stress Ulcer Prophylaxis (ICU)

  • For mechanical ventilation > 48 h, coagulopathy
  • PPI or H2 RA
  • Stop when no longer needed

349.3.3.12 Gastric Cancer + H. pylori

  • Major risk factor
  • H. pylori eradication reduces risk
  • Gastric atrophy + intestinal metaplasia surveillance

349.3.3.13 MALT Lymphoma + H. pylori

  • Eradication of H. pylori → 70-80% regression
  • Gastric MALT lymphoma low-grade
  • Surveillance EGD

349.3.3.14 Vonoprazan Drug Interactions

  • Less CYP2C19 dependence
  • Different metabolism

349.3.4 Pearls

  • PUD: H. pylori most common; NSAID in developed
  • DU pain relieved by food; GU worsened; biopsy GU
  • Quadruple therapy preferred (rising clarithromycin resistance)
  • Vonoprazan-based new option (FDA 2022)
  • Functional dyspepsia: PPI + H. pylori + TCA
  • ZES: gastrin > 1000 + MEN1 + multiple atypical ulcers
  • PPI long-term side effects: B12, Mg, C. diff, fractures (concerns)