Generic Medicine Info
Indications and Dosage
Eradication of H. pylori associated with peptic ulcer disease, Gastric and duodenal ulcers, Gastro-oesophageal reflux disease, NSAID-associated ulceration
Adult: 40 mg once daily given via infusion over 20-30 minutes until oral administration is possible.

Zollinger-Ellison syndrome
Adult: Initially, 60 mg daily via infusion over 20-30 minutes, adjust dose according to response. Daily doses >60 mg should be given in 2 divided doses.

NSAID-associated ulceration
Adult: 20 mg once daily for up to 8 weeks. Maintenance: 20 mg once daily.

Eradication of H. pylori associated with peptic ulcer disease
Adult: 20 mg bid for 1 week in combination with clarithromycin and with either amoxicillin or metronidazole. Alternatively, 40 mg once daily for 1 week in combination with amoxicillin and metronidazole.
Child: >4 years 15-30 kg: 10 mg bid. 31->40 kg: 20 mg bid. All doses are given in combination with amoxicillin and clarithromycin for 1 week.

Peptic ulcer
Adult: 20 mg or 40 mg once daily. Treatment duration: 4 weeks (duodenal ulcer); 8 weeks (gastric ulcer). Maintenance: 10-20 mg once daily, may increase up to 40 mg according to response.

Gastro-oesophageal reflux disease
Adult: 20 mg once daily for 4-8 weeks. For severe case: 40 mg once daily for 8 weeks. Maintenance: 10 mg once daily, may increase to 20-40 mg once daily if necessary.
Child: ≥1 year weighing 10-20 kg: 10 mg once daily, increased to 20 mg once daily if necessary. ≥2 years weighing >20 kg: 20 mg once daily, increased to 40 mg once daily if necessary. Treatment duration: 4-8 weeks.

Zollinger-Ellison syndrome
Adult: Initially, 60 mg daily, adjust as required. Usual dose: 20-120 mg daily. Dose >80 mg should be given in 2 divided doses.
Special Patient Group

CYP2C19 is the main enzyme responsible in omeprazole metabolism. CYP2C19 polymorphism test can be considered to identify individuals who may require dose adjustment or experience treatment failure. The incidence of CYP2C19 poor metaboliser is markedly higher in Asians. 15 to 20% of Asians have reduced or absent CYP2C19 enzyme activity.

Ultrarapid metabolisers (carriers of 2 increased function alleles *17/*17)

Eradication of H. pylori: Increase dose by 100-200%. Monitor for risks of therapeutic failure.
Hepatic Impairment
10-20 mg daily.
Cap: Should be taken with food. Take immediately before a meal.
Mups Tab: May be taken with or without food.
Powd For Oral Susp: Should be taken on an empty stomach. Take at least 1 hr before a meal.
Delayed-Release Cap: Should be taken on an empty stomach. Take at least 1 hr before meals. Swallow whole, do not chew/crush. For patients w/ difficulty swallowing, cap may be carefully opened & entire contents sprinkled in a spoonful of applesauce. Swallow drug/food mixt w/o chewing immediately after prep. Drug/food mixt should not be stored for future use.
IV infusion: Reconstitute with 100 mL of dextrose 5% or NaCl 0.9% inj.
Concomitant use with nelfinavir.
Special Precautions
Patient with reduced body store or risk factors for reduced vitamin B12 absorption; risk of osteoporosis. Hepatic impairment. Children, elderly. Pregnancy and lactation. CYP2C19 ultrarapid metabolisers.
Adverse Reactions
Significant: Hypomagnasaemia, cutaneous lupus erythematosus, SLE, osteoporosis-related fractures, fundic gland polyp, carcinoma, Clostridium difficile-associated diarrhoea, interstitial nephritis, Vitamin B12 deficiency (long-term therapy), gastrointestinal infection (e.g. salmonella, Campylobacter).
Gastrointestinal disorders: Nausea, vomiting, diarrhoea, constipation, flatulence, abdominal pain.
General disorders and administration site conditions: Weakness, malaise.
Hepatobiliary disorders: Increased liver enzymes.
Immune system disorders: Urticaria.
Metabolism and nutrition disorders: Peripheral oedema.
Musculoskeletal and connective tissue disorders: Back pain.
Nervous system disorders: Headache, dizziness, somnolence, paraesthesia, vertigo.
Psychiatric disorders: Insomnia.
Respiratory, thoracic and mediastinal disorders: Cough.
Skin and subcutaneous tissue disorders: Rash, dermatitis, pruritus.
Monitoring Parameters
Rule out gastric malignancy prior to initiation of treatment. Monitor Mg concentrations prior to initiation and periodically thereafter.
Symptoms: Nausea, vomiting, dizziness, abdominal pain, diarrhoea, headache apathy, depression and confusion. Management: Symptomatic and supportive treatment.
Drug Interactions
May decrease plasma concentrations of nelfinavir and atazanavir. Increased risk of hypomagnesaemia with diuretics. May increase plasma concentration of tacrolimus, methotrexate. May decreased absorption of itraconazole, ketoconazole, posaconazole, erlotinib. May decrease metabolism of diazepam, phenytoin, cilostazol. May reduce the antiplatelet activity of clopidogrel. May increase bioavailability of digoxin.
Food Interaction
Decreased serum concentration with St John's wort.
Lab Interference
May cause false-positive result in diagnostic tests for neuroendocrine tumours.
Description: Omeprazole is a substituted benzimidazole gastric antisecretory agent and is also known as proton pump inhibitor (PPI). It blocks the final step in gastric acid secretion by specific inhibition of adenosine triphosphatase (ATPase) enzyme system present on the secretory surface of the gastric parietal cell. Both basal and stimulated acid are inhibited.
Onset: Antisecretory: Approx 1 hour.
Duration: Up to 72 hours.
Absorption: Rapid but variably absorbed from the gastrointestinal tract. Bioavailability: Approx 30-40%. Time to peak plasma concentration: 0.5-3.5 hours.
Distribution: Enters breast milk. Plasma protein binding: Approx 95%.
Metabolism: Metabolised in the liver primarily by CYP2C19 isoenzyme to hydroxyl-omeprazole; and lesser extent by CYP3A4 to omeprazole sulfone.
Excretion: Mainly via urine (approx 77% as metabolites, small amount as unchanged drug); faeces (small amount). Elimination half-life: 0.5-3 hour.
Chemical Structure

Chemical Structure Image

Source: National Center for Biotechnology Information. PubChem Database. Omeprazole, CID=4594, (accessed on Jan. 22, 2020)

Store below 25°C. Protect from light and moisture.
MIMS Class
Antacids, Antireflux Agents & Antiulcerants
ATC Classification
A02BC01 - omeprazole ; Belongs to the class of proton pump inhibitors. Used in the treatment of peptic ulcer and gastro-oesophageal reflux disease (GERD).
Dean L. Omeprazole Therapy and CYP2C19 Genotype. Medical Genetics Summaries [Internet]. Bethesda (MD): National Center for Biotechnology Information (US). 2012 Oct. PMID: 28520353

Annotation of DPWG Guideline for Omeprazole and CYP2C19. Pharmacogenomics Knowledgebase (PharmGKB). Accessed 06/02/2019.

Annotation of FDA Label for Omeprazole and CYP2C19. Pharmacogenomics Knowledgebase (PharmGKB). Accessed 06/02/2019.

Anon. CYP2C19 - Omeprazole (Pharmacogenomics). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. Accessed 06/02/2019.

Anon. Omeprazole. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. Accessed 06/02/2019.

Anon. Omeprazole. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. Accessed 06/02/2019.

Buckingham R (ed). Omeprazole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. Accessed 06/02/2019.

Omeprazole - Overview. Pharmacogenomics Knowledgebase (PharmGKB). Accessed 06/02/2019.

Prilosec (AstraZeneca Pharmaceuticals LP). U.S. FDA. Accessed 06/02/2019.

Disclaimer: This information is independently developed by MIMS based on Omeprazole from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2022 MIMS. All rights reserved. Powered by
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