Omeprazole, a substituted benzimidazole, is an inhibitor of gastric acid secretion. It inhibits gastric acid secretion by blocking hydrogen-potassium-adenosine triphosphatase (H⁺/K⁺ ATPase) enzyme system in the gastric parietal cell. After oral administration, the onset of the antisecretory effect occurs within one hour, with the maximum effect occurring within two hours and inhibition of secretion lasts up to 72 hours. When the drug is discontinued, secretory activity returns gradually, over 3 to 5 days.

Omeprazole is indicated for the treatment of-

• Gastric and duodenal ulcer
• NSAID-associated duodenal and gastric ulcer
• As prophylaxis in patients with a history of NSAID-associated duodenal and gastric ulcer
• Gastro-esophageal reflux disease
• Long-term management of acid reflux disease
• Acid-related dyspepsia
• Severe ulcerating reflux esophagitis
• Prophylaxis of acid aspiration during general anesthesia
• Zollinger-Ellison syndrome
• Helicobacter pylori-induced peptic ulcer.

Oral-

• Benign gastric and duodenal ulcer: 20 mg once daily for 4 weeks in duodenal ulceration, 8 weeks in gastric ulceration; in severe or recurrent cases, dose to be increased to 40 mg daily; maintenance dose for recurrent duodenal ulcer, 20 mg once daily; in prevention of relapse in duodenal ulcer, 10-20 mg daily.
• NSAID-associated duodenal or gastric ulcer: 20 mg once daily for 4 weeks, continued for further 4 weeks, if not fully healed. 20 mg once daily is used as prophylaxis in patients with a history of NSAID-associated duodenal or gastric ulcers.
• Gastro-esophageal reflux disease: 20 mg once daily for 4 weeks, continued for further 4-8 weeks, if not fully healed; 40 mg once daily has been given for 8 weeks in gastro-esophageal reflux disease, refractory to other treatment; maintenance dose is 20 mg once daily.
• Long-term management of acid reflux disease: 10-20 mg daily.
• Acid-related dyspepsia: 10-20 mg once daily for 2-4 weeks.
• Prophylaxis of acid aspiration: 40 mg on the preceding evening, then 40 mg 2-6 hours before surgery.
• Zollinger-Ellison syndrome: Initially 60 mg once daily; usual range 20-120 mg daily (If daily dose is more than 80 mg, 2 divided dose should be used).
• Helicobacter pylori eradication regimen in peptic ulcer disease: Omeprazole is recommended at a dose of 20 mg twice daily in association with antimicrobial agents as detailed below: Amoxicillin 500 mg and Metronidazole 400 mg both three times a day for one week, or Clarithromycin 250 mg and Metronidazole 400 mg both twice a day for one week, or Amoxicillin 1 g and Clarithromycin 500 mg both twice a day for one week.
• Paeditaric use in severe ulcerating reflux esophagitis (Child>1 year): If body-weight 10-20 kg, 10-20 -mg once daily for 4-12 weeks; if body-weight over 20 kg, 20-40 mg once daily for 4-12 weeks.

IV Injection-

• Prophylaxis of acid aspiration: Omeprazole 40 mg to be given slowly (over a period of 5 minutes) as an intravenous injection, one hour before surgery.
• Duodenal ulcer, gastric ulcer or reflux oesophagitis: In patients with duodenal ulcer, gastric ulcer or reflux oesophagitis where oral medication is inappropriate, Omeprazole IV 40 mg once daily is recommended.
• Zollinger- Ellison syndrome (ZES): In patients with Zollinger-Ellison Syndrome the recommended initial dose of Omeprazole given intravenously is 60 mg daily. Higher daily doses may be required and the dose should be adjusted individually. When doses exceed 60 mg daily, the dose should be divided & given twice daily.

Administration

Direction for use of IV Injection: Omeprazole lyophilized powder and water for injection is for intravenous administration only and must not be given by any other route. Omeprazole IV injection should be given as a slow intravenous injection. The solution for IV injection is obtained by adding 10 ml water for injection to the vial containing powder. After reconstitution the injection should be given slowly over a period of at least 2 to 5 minutes at a maximum rate of 4 ml/minute. Use only freshly prepared solution. The solution should be used within 4 hours of reconstitution.

Direction for use of IV Infusion: Omeprazole IV infusion should be given as an intravenous infusion over a period of 20-30 minutes or more. The contents of one vial must be dissolved in 100 ml saline for infusion or 100 ml 5% Dextrose for infusion. The solution should be used within 12 hours when Omeprazole is dissolved in saline and within 6 hours when dissolved in 5% Dextrose. The reconstituted solution should not be mixed or co-administered in the same infusion set with any other drug.

Omeprazole is contraindicated in patients with known hypersensitivity to any of the components of the formulation.

Omeprazole is generally well tolerated. Nausea, abdominal colic, paresthesia, dizziness and headache have been stated to be generally mild and transient and not requiring a reduction in dosage.

When gastric ulcer is suspected, the possibility of gastric malignancy should be excluded before treatment with Omeprazole is instituted, as treatment may alleviate the symptoms and delay diagnosis.

Pregnancy & Lactation

US FDA pregnancy category of Omeprazole is C. However, results from three prospective epidemiological studies indicate no adverse effects of Omeprazole on pregnancy or on the health of the fetus/newborn child. There is no information available on the passage of Omeprazole into breast milk or its effects on the neonate. Breast-feeding should, therefore, be discontinued, if the use of Omeprazole is considered essential.