Omeprazole: Indication, Dosage, Side Effect, Precaution

Generic Medicine Info Patient Medicine Information

This information is not country-specific. Please refer to the Myanmar prescribing information.

Generic Medicine Info

Indications and Dosage

Intravenous
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.

Intravenous
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.

Oral
NSAID-associated ulceration

Adult: 20 mg once daily for up to 8 weeks. Maintenance: 20 mg once daily.

Oral
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.

Oral
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.

Oral
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.

Oral
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

Pharmacogenomics:

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.

Administration

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.

Reconstitution

IV infusion: Reconstitute with 100 mL of dextrose 5% or NaCl 0.9% inj.

Contraindications

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.

Pregnancy Category (US FDA)

PO: C

Monitoring Parameters

Rule out gastric malignancy prior to initiation of treatment. Monitor Mg concentrations prior to initiation and periodically thereafter.

Overdosage

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.

Action

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.
Pharmacokinetics:
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

Storage

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).

References

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). https://www.pharmgkb.org. Accessed 06/02/2019.

Annotation of FDA Label for Omeprazole and CYP2C19. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org/. Accessed 06/02/2019.

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

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

Anon. Omeprazole. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 06/02/2019.

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

Omeprazole - Overview. Pharmacogenomics Knowledgebase (PharmGKB). https://www.pharmgkb.org/. Accessed 06/02/2019.

Prilosec (AstraZeneca Pharmaceuticals LP). U.S. FDA. https://www.fda.gov/. Accessed 06/02/2019.

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