Omeprazole: clinical use

Prescribing considerations

• Review the indication periodically, particularly during prolonged treatment.
• Investigate dysphagia, recurrent vomiting, gastrointestinal bleeding or significant unintentional weight loss rather than masking them with acid suppression.
• Consider reduced vitamin B12 absorption, gastrointestinal infection and fracture risk during prolonged treatment, particularly with additional risk factors.
• Check formulation-specific excipients and administration requirements; oral liquids may contain clinically relevant sodium, potassium, sugars or preservatives.
• Omeprazole may interfere with chromogranin A testing and affect investigations of upper gastrointestinal symptoms.

Contraindications and cautions

• Hypersensitivity to omeprazole, another substituted benzimidazole or a product excipient.
• Concomitant nelfinavir treatment.
• Use additional caution with severe hepatic impairment, suspected malignancy, previous severe PPI-related skin reactions and medicines affected by gastric pH or CYP2C19 inhibition.

Monitoring

• Consider magnesium before and during prolonged treatment in people taking digoxin, diuretics or other medicines that can lower magnesium, or when symptoms suggest deficiency.
• Consider vitamin B12 status during prolonged treatment when stores are low or absorption is impaired.
• Use medicine-specific monitoring for interacting drugs such as tacrolimus, phenytoin, digoxin or vitamin K antagonists.
• Assess renal function if tubulointerstitial nephritis is suspected and review persistent diarrhoea for infectious or microscopic colitis causes.

Clinical pharmacology

Omeprazole is an acid-labile, enterically protected PPI. After absorption it concentrates in parietal-cell canaliculi and irreversibly inhibits active proton pumps. It is extensively metabolised mainly through CYP2C19 and CYP3A4 and also inhibits CYP2C19.

Formulation and product differences

• Gastro-resistant tablets must be swallowed intact and are unsuitable for crushing.
• Selected capsules contain enteric-coated pellets; some may be opened if the pellets remain intact.
• The selected powder for oral suspension requires constitution, shaking and measurement with an oral syringe, with product-specific food, storage, electrolyte and enteral-tube considerations.
• Lappoxo has product-specific preparation and administration instructions.
• The pharmacy non-prescription tablet is licensed only for adult reflux symptoms, while prescription products cover broader indications and selected paediatric use.

Capsule

Route: Oral

Strengths: 10 mg, 20 mg, 40 mg

Gastro-resistant capsule

Route: Oral

Strengths: 10 mg, 20 mg, 40 mg