Proton Pump Inhibitors

PPIs: Intro & MOA - Pump Stoppers!

• Most potent suppressors of gastric acid secretion.
• Commonly used: Omeprazole, Lansoprazole, Pantoprazole, Esomeprazole, Rabeprazole.
• Mechanism of Action (MOA):
  • Prodrugs: Administered in inactive form.
  • Accumulate in acidic parietal cell canaliculi (pH < 4).
  • Convert to active sulfenamide metabolite via H+ catalyzed process.
  • Irreversibly bind to cysteine residues of the H+/K+ ATPase (proton pump).
  • Inhibits final step in gastric acid ($H^+$) secretion pathway.
  • Effect lasts 24-48 hours until new pumps are synthesized.

⭐ PPIs cause irreversible inhibition of the H+/K+ ATPase (proton pump) in parietal cells.

PPIs: Pharmacokinetics - Body's Journey

• Absorption (Oral):
  • Prodrugs: Enteric-coated, delayed-release (bypass stomach acid).
  • Site: Duodenum.
  • Food ↓ absorption; take 30-60 min pre-meal.
  • Bioavailability: Variable (omeprazole ~30-40% initially), ↑ with repeated doses.
• Distribution & Activation:
  • Highly protein-bound (>95%).
  • Concentrate in parietal cell canaliculi.

  ⭐ PPIs are prodrugs; require activation by acid in parietal cell canaliculi to active form.

• Metabolism:
  • Hepatic: CYP2C19 (major, genetic polymorphism) & CYP3A4 (minor).
• Excretion:
  • Renal (inactive metabolites).
  • Short plasma $t_{1/2}$ (~1-2h); long action (irreversible H+/K+ ATPase binding).

PPIs: The Line-Up - Meet the Crew

Key Proton Pump Inhibitors (PPIs) used clinically, with typical adult daily doses and distinguishing characteristics:

PPIs: Clinical Uses - Healing Power

• Gastroesophageal Reflux Disease (GERD): First-line, superior for healing esophagitis and symptom relief.
• Peptic Ulcer Disease (PUD):
  • Healing gastric and duodenal ulcers.
  • Part of H. pylori eradication regimens.
• Zollinger-Ellison Syndrome: Drug of choice for hypersecretory states.
• Stress Ulcer Prophylaxis: In high-risk ICU patients.
• NSAID-associated Ulcers: Prevention and treatment.
• Eosinophilic Esophagitis: Effective for symptomatic and histologic improvement.
• Functional Dyspepsia: For persistent symptoms.

⭐ PPIs are the most effective drugs for treating GERD and healing peptic ulcers.

PPIs: Adverse Effects & Interactions - Caution Zones

• Common: Headache, diarrhea, nausea.
• Long-term Risks:
  • Nutrient deficiencies: ↓Vit B12, ↓Mg (hypomagnesemia), ↓Ca (↑fracture risk).
  • Infections: ↑Clostridium difficile, ↑pneumonia.
  • Kidney: Acute Interstitial Nephritis (AIN).
  • Gastric: Fundic gland polyps; atrophic gastritis.

⭐ Long-term PPI use is associated with increased risk of osteoporotic fractures, Clostridium difficile infection, and hypomagnesemia.

• Key Drug Interactions:
  • Omeprazole/Esomeprazole (CYP2C19 inhibitors): ↓clopidogrel efficacy. ⚠️
  • Altered pH: ↓absorption of ketoconazole, iron, some ARVs.
  • ↑Methotrexate toxicity.
• Caution: Elderly; prolonged use (>1 year).

High‑Yield Points - ⚡ Biggest Takeaways

• Most potent inhibitors of gastric acid secretion; irreversibly block H+/K+ ATPase.
• Prodrugs, activated in parietal cell canaliculus; take 30-60 min before meals.
• Uses: GERD, PUD, Zollinger-Ellison syndrome, H. pylori eradication regimens.
• Long-term: ↑ risk of fractures, hypomagnesemia, C. difficile infection, pneumonia, Vit B12 deficiency.
• Omeprazole inhibits CYP2C19, notably reducing clopidogrel efficacy.
• Examples: Omeprazole, Pantoprazole, Lansoprazole, Esomeprazole.