Drug Guide
Omeprazole
Classification
Therapeutic: Gastrointestinal agent
Pharmacological: Proton pump inhibitor
FDA Approved Indications
- Erosive esophagitis
- Gastroesophageal reflux disease (GERD)
- Duodenal ulcer disease
- Pathologic hypersecretory conditions (including Zollinger-Ellison syndrome)
Mechanism of Action
Omeprazole irreversibly inhibits the H+/K+ ATPase enzyme system of the gastric parietal cells, thereby suppressing gastric acid secretion.
Dosage and Administration
Adult: 20-40 mg once daily before a meal. Duration varies by condition.
Pediatric: Typically, 10-20 mg once daily; dosage depends on age and condition.
Geriatric: Starting dose should be cautious, usually 20 mg daily; monitor for increased risk of adverse effects.
Renal Impairment: No specific dose adjustment is generally required, but caution is advised.
Hepatic Impairment: Use with caution; start with lower doses.
Pharmacokinetics
Absorption: Well absorbed orally with about 35-40% bioavailability.
Distribution: Extensively distributed; protein bound (~95%).
Metabolism: Primarily hepatic via CYP2C19 and CYP3A4 enzymes.
Excretion: Renally and fecally excreted; approximately 80% eliminated in urine.
Half Life: 0.5 to 1 hour; however, acid suppression lasts longer due to irreversible enzyme inhibition.
Contraindications
- Hypersensitivity to omeprazole or similar compounds.
Precautions
- Use cautiously in patients on warfarin, methotrexate, or at high risk of fractures, Clostridium difficile-associated diarrhea, pneumonia, etc.
Adverse Reactions - Common
- Headache (Common)
- Nausea/Vomiting (Common)
- diarrhea (Common)
- Abdominal pain (Common)
Adverse Reactions - Serious
- Clostridioides difficile-associated diarrhea (Less common)
- Hypomagnesemia (Rare)
- Bone fractures (with long-term use) (Rare)
- Seizures (due to severe hypomagnesemia) (Rare)
Drug-Drug Interactions
- Clopidogrel (may reduce its efficacy), warfarin (may increase bleeding risk), atazanavir, rilpivirine.
Drug-Food Interactions
- Juice may increase absorption—though not typically significant.
Drug-Herb Interactions
- St. John’s Wort may reduce efficacy of omeprazole.
Nursing Implications
Assessment: Assess for symptoms of GERD, peptic ulcers, and potential side effects.
Diagnoses:
- Risk for infections (e.g., C. difficile), risk for osteoporosis/fractures.
- Impaired gastrointestinal functioning.
Implementation: Administer before meals, usually once daily. Monitor for effectiveness and adverse reactions.
Evaluation: Symptom relief, healing observed via endoscopy if applicable.
Patient/Family Teaching
- Take medication exactly as prescribed, preferably before meals.
- Report persistent or severe side effects, diarrhea, or signs of infection.
- Avoid alcohol, smoking, and NSAIDs unless directed.
- Discuss potential long-term risks (e.g., fractures, hypomagnesemia).
Special Considerations
Black Box Warnings:
- Increased risk of Clostridioides difficile-associated diarrhea.
- Risk of fractures with long-term use.
Genetic Factors: CYP2C19 polymorphisms can affect metabolism and efficacy.
Lab Test Interference: Can interfere with CYP2C19 substrate drugs, impacting therapeutic levels.
Overdose Management
Signs/Symptoms: Rare, but could include nausea, vomiting, sweating, blurred vision.
Treatment: Supportive care; no specific antidote. Dialysis unlikely to be effective due to high protein binding.
Storage and Handling
Storage: Store at room temperature, 20-25°C (68-77°F).
Stability: Stable for 2-3 years when stored properly.