Proton Pump Inhibitors
Proton pump inhibitors irreversibly block the gastric H+/K+-ATPase, providing the most potent suppression of acid secretion available. They are essential in GERD, peptic ulcer disease, and Zollinger-Ellison syndrome.
## Mechanism of Action
Proton pump inhibitors (PPIs) are prodrugs that accumulate in the acidic environment of parietal cell canaliculi, where they are converted to active sulfenamide metabolites. These metabolites form covalent disulfide bonds with cysteine residues on the H+/K+-ATPase (proton pump), irreversibly inactivating it. Since the proton pump is the final step in acid secretion, PPIs provide more complete and prolonged acid suppression than H2-receptor antagonists.
New proton pump synthesis is required to restore acid secretion, which takes 24-48 hours. Maximum efficacy is achieved after 3-5 days of continuous dosing as the steady-state turnover of pumps is reached.
## Available PPIs
Omeprazole, esomeprazole, lansoprazole, pantoprazole, rabeprazole, and dexlansoprazole are the currently available agents. They have comparable efficacy at equivalent doses. Esomeprazole (the S-enantiomer of omeprazole) and dexlansoprazole offer marginally more consistent acid suppression but no meaningful clinical superiority for most patients.
PPIs should be taken 30-60 minutes before a meal, as they only inhibit actively secreting proton pumps stimulated by food intake. Taking them at bedtime without a meal reduces effectiveness.
## Clinical Indications
- **GERD** -- 4-8 week course for erosive esophagitis; maintenance therapy for Barrett's esophagus.
- **Peptic ulcer disease** -- Accelerates healing of gastric and duodenal ulcers; essential in H. pylori triple therapy.
- **NSAID gastroprotection** -- Co-prescribed with long-term NSAIDs in high-risk patients.
- **Zollinger-Ellison syndrome** -- High-dose PPIs are the treatment of choice for gastrin-secreting tumors.
- **Stress ulcer prophylaxis** -- Used in critically ill ICU patients at risk for GI bleeding.
## Long-Term Risks
Prolonged PPI use (>1 year) has been associated with several concerns, though causality remains debated for most:
- **Hypomagnesemia** -- Can cause muscle cramps, arrhythmias, and seizures. Monitor in patients on long-term therapy.
- **Fracture risk** -- Modest increase in hip fractures, possibly related to reduced calcium absorption.
- **C. difficile infection** -- Reduced gastric acidity may allow pathogen survival. Risk is additive with antibiotics.
- **Vitamin B12 deficiency** -- Acid is needed for B12 release from food proteins. Clinically relevant after years of use.
- **Kidney disease** -- Observational data suggest increased risk of chronic kidney disease and acute interstitial nephritis.
## Deprescribing
Many patients remain on PPIs longer than necessary. Guidelines recommend periodic reassessment. For patients on PPIs for uncomplicated GERD, a step-down approach works well: reduce dose, switch to H2-blocker (famotidine), or trial discontinuation with on-demand use. Abrupt cessation can cause rebound acid hypersecretion lasting 2-4 weeks.
## Key Takeaways
- PPIs are the most effective acid-suppressing drugs, acting via irreversible proton pump inhibition.
- Take PPIs before meals for optimal efficacy -- timing matters.
- Long-term use requires periodic reassessment of ongoing need and monitoring for hypomagnesemia.
- Deprescribing is safe and appropriate for many patients using PPIs beyond their indicated duration.