Omeprazole

Omeprazole is a prototype member of the substituted benzimidazoles, which inhibit the final common step in gastric acid secretion. It is hence a proton pump inhibitor.

It has a dose-dependent suppression of gastric acid secretion without the anticholinergic or H2 blocking action.

Omeprazole is inactive at neutral pH.

Mechanism of action.

• It binds to H+/K+-exchanging ATPase (proton pump) in gastric parietal cells, suppressing basal and stimulating acid secretion in the body.

Clinical uses.

• Peptic ulcer: The relief of pain is rapid and excellent.
• Bleeding peptic ulcer.
• Stress ulcers.
• Zollinger-Ellison syndrome
• Gastroesophageal reflux disease (GERD): rapid relief of symptoms. Higher doses than for peptic ulcers or twice-daily administration are recommended.
• Aspiration pneumonia: PPIs are an alternative to H2 blockers for preventing aspiration pneumonia due to prolonged anesthesia.

Adverse effects.

• Nausea, loose stools, headache, abdominal pain, muscle, and joint pain.
• Dizziness, rash, leucopenia, and hepatic dysfunction.
• Gastritis and hypergastrinemia.
• Malaise, alopecia, myalgia
• Hepatitis
• Peripheral edema, gynecomastia, and erectile dysfunction.

Drug interaction.

• Reduced gastric acidity causes a decrease in the absorption of ketoconazole and iron salts.
• It inhibits the oxidation of diazepam, phenytoin, and warfarin; hence, their levels may increase.
• It interferes with the activation of clopidogrel by inhibiting CYP2C19.
• Clarithromycin inhibits omeprazole metabolism and increases its plasma concentration.

Dosage.

• OMIZAC, NILSEC 20 mg capsule.
• OMEZ, OCID, OMEZOL 10, 20mg capsules,
• PROTOLOC 20, 40 mg capsules containing enteric-coated granules.
• Capsules must not be opened or chewed, or taken in the morning before meals.