Omeprazole is indicated for the short-term treatment of peptic ulcer disease in adults where most patients heal within four weeks.  Patients with duodenal ulcer disease and H. pylori infection disease that is active for up to one year may benefit from combination therapy that includes omeprazole with clarithromycin, amoxicillin, and metronidazole.

Studies show a reduction in recurrence of duodenal ulcers with H. pylori treatment and a reduced rate of clarithromycin resistance with quadruple therapy.[1][2]  Clinicians should expect antimicrobial resistance and susceptibility testing performed if patients fail treatment, and treatment adjusted accordingly.

Omeprazole indications also include gastric ulcers in adults, and gastroesophageal reflux disease in adults and pediatric populations. Studies have shown the efficacy of omeprazole for short term treatment in erosive esophagitis.[3][4]  Omeprazole is also indicated for healing erosive esophagitis in both adults and children.  Conditions prone to hypersecretion such as Zollinger-Ellison syndrome, multiple endocrine adenomas, and systemic mastocytosis also respond to management with omeprazole treatment in adults. 

Omeprazole is a proton pump inhibitor. It inhibits the parietal cell H+ / K+ ATP pump, the final step of acid production. In turn, omeprazole suppresses gastric basal and stimulated acid secretion. The inhibitory effects of omeprazole occur rapidly within 1 hour of administration, with the maximum effect occurring in 2 hours. The inhibitory effects last for approximately 72 hours after administration, followed by a return to baseline activity in 3 to 5 days. With daily use of the medication, the effects will plateau at four days.

Omeprazole metabolism occurs via the hepatic cytochrome P450 enzyme system; the two primary CYP isozymes involved are CYP2C19 and CYP3A4.  Urinary excretion is a primary route of excretion of omeprazole metabolites.  Omeprazole has a short half-life of a half-hour to an hour in healthy subjects and about three hours for patients with hepatic impairment, but its pharmacological effect lasts much longer since it preferentially concentrates in parietal cells where it forms a covalent linkage with H+/K+ ATPase, which it irreversibly inhibits.[5] 

The method of delivery for omeprazole is heavily dependent on the diagnosis.

For H. pylori infection, the recommended adult oral regimen is 20 mg plus clarithromycin 500 mg plus amoxicillin 1000 mg plus metronidazole 500 mg, each given twice daily for fourteen days. If an ulcer is present on initial diagnosis, then it is recommended to provide an additional 18 days of omeprazole 20 mg once daily

The recommended oral adult dose for the treatment of symptomatic GERD absent esophageal lesions is 20 mg daily for up to 4 weeks. However, if erosive lesions are present, therapy may extend to 8 weeks.

The recommendation for patients with hypersecretory diseases is to start at 60 mg once daily, followed by the individualization of dosage based on the patient's need and clinical response. If the daily dose is higher than 80 mg, they should divide the dosage throughout the day.  Long term treatment with omeprazole is not recommended, and eventually, switching to an H2-inhibitor is preferred.

For pediatric patients between the ages of 1 and 16, the dosage is dependent on the weight of the child.

• Weight: 5 less than 10 kg, dose: 5 mg
• Weight between 10 and 20 kg, dose: 10 mg
• Weight: over 20 kg, dose: 20 mg

Omeprazole should be ingested 30 to 60 minutes before meals. It may be taken with antacids. When taken twice daily, the first dose should be before breakfast and the second dose before dinner. The capsule and tablet should be swallowed whole, not crushed or chewed. However, it is permissible to open the capsule and mix the contents with one tablespoon of applesauce, soft enough to be swallowed without chewing. The suspension should be left to thicken for two to three minutes, following reconstitution and administered within 30 minutes.  Drink with a glass of cool water to ensure complete swallowing of the pellets.

Omeprazole therapy should be at the lowest dose possible for the shortest duration; physicians have looked into deprescribing proton pump inhibitors if patients are on it long term. One group recommends deprescribing PPIs, meaning to reduce the dose, stop completely, or use "on-demand" dosing in adults who have completed a minimum of 4 weeks of PPI treatment for heartburn or mild to moderate gastroesophageal reflux disease or esophagitis, and who have achieved symptomatic resolution. The patient should follow up for monitoring of symptoms at weeks 4 and 12 and again at 6 to 12 months. But these recommendations do not apply to those who have or have had Barrett's esophagus, severe esophagitis grade C or D, or documented history of bleeding gastrointestinal ulcers.[6]

Omeprazole is considered a benign drug; however, the primary adverse effects of omeprazole include headache, abdominal pain, nausea, diarrhea, vomiting, and flatulence in adults. The major adverse effects in the pediatric population are similar to adults; the most frequent events were reportedly fever and respiratory.  Proton pump inhibitors (PPI) therapy may correlate with an increased risk of Clostridioides difficile (C. diff) associated diarrhea.[7]  Long-term and multiple daily dose PPI treatment may have connections with an increased risk for osteoporosis-related fractures of the hip, wrist, or spine but newer studies show long-term PPI use does not correlate with any changes in bone mineral density or bone strength that would predispose to an increased risk of fracture suggesting this relationship is not casual.[8][9]. Some evidence has shown a diminished antiplatelet activity of clopidogrel due to impaired CYP2C19 function when used in conjunction with 80 mg omeprazole.[10] There are rare reports of hypomagnesemia with prolonged treatment with PPIs.[11] Avoid concomitant use of omeprazole with St John’s wort or rifampin and other CYP450 inducers due to the potential reduction in omeprazole concentration. 

Omeprazole is contraindicated in patients with a history of hypersensitivity to the drug or dosage form. It is also contraindicated in patients taking dosage forms containing rilpivirine.