Overview
Omeprazole is a proton pump inhibitor (PPI) that suppresses gastric acid secretion by irreversibly inhibiting the H+/K+ ATPase enzyme system at the secretory surface of gastric parietal cells. It is used for the treatment of gastroesophageal reflux disease (GERD), erosive esophagitis, peptic ulcer disease, and Helicobacter pylori eradication in combination with antibiotics. The drug provides long-lasting acid suppression with once-daily dosing.
Mechanism of Action
Omeprazole is a substituted benzimidazole that suppresses gastric acid secretion by specific inhibition of the H+/K+ ATPase enzyme system at the secretory surface of gastric parietal cells. It blocks the final step of acid production, resulting in prolonged inhibition of basal and stimulated acid secretion regardless of the stimulus.
Indications
- Treatment of gastroesophageal reflux disease (GERD)
- Healing of erosive esophagitis
- Maintenance of healing of erosive esophagitis
- Treatment of active duodenal ulcer
- Treatment of active benign gastric ulcer
- Pathological hypersecretory conditions (e.g., Zollinger-Ellison syndrome)
- Helicobacter pylori eradication in combination with clarithromycin and amoxicillin
Common Doses
- 10 mg
- 20 mg
- 40 mg
Dosage
Typical adult dosage is 20-40 mg once daily before eating. For GERD: 20 mg daily for 4-8 weeks. For erosive esophagitis healing: 20-40 mg daily for 4-8 weeks. For H. pylori eradication: 20 mg twice daily with clarithromycin and amoxicillin for 10-14 days. Doses up to 120 mg three times daily may be required for Zollinger-Ellison syndrome.
Contraindications
- Known hypersensitivity to omeprazole, substituted benzimidazoles, or any component of the formulation
- Concomitant use with rilpivirine-containing products
Side Effects
- Headache
- Abdominal pain
- Nausea
- Diarrhea
- Vomiting
- Flatulence
- Acute tubulointerstitial nephritis
- Clostridium difficile-associated diarrhea
- Bone fracture
- Cutaneous and systemic lupus erythematosus
- Vitamin B12 deficiency
- Hypomagnesemia
- Fundic gland polyps
Interactions
- Rilpivirine: Contraindicated due to decreased exposure
- Atazanavir and nelfinavir: Avoid concomitant use
- Clopidogrel: Avoid concomitant use due to reduced antiplatelet effect
- Warfarin: Monitor INR and prothrombin time
- Methotrexate: May increase serum concentrations
- Citalopram: Limit dose to 20 mg daily
- Cilostazol: Reduce dose to 50 mg twice daily
- Phenytoin: Monitor serum concentrations
- Diazepam: Monitor for increased sedation
- Digoxin: Monitor concentrations
- Drugs dependent on gastric pH for absorption (e.g., iron salts, ketoconazole)
- Tacrolimus: Monitor whole blood concentrations
Counseling Points
- Take before eating, typically before breakfast
- Swallow capsules whole; do not crush, chew, or open
- For patients with difficulty swallowing, capsules can be opened and sprinkled on applesauce
- Report severe diarrhea, abdominal pain, or signs of kidney problems
- Long-term use may require monitoring of magnesium and vitamin B12 levels
- Do not take with rilpivirine-containing HIV medications