Omeprazole is a proton pump inhibitor (PPI) that suppresses gastric acid secretion by irreversibly inhibiting the H+/K+-ATPase (“proton pump”) in parietal cells. After absorption in the small intestine, it concentrates in the acidic canaliculi of parietal cells and is converted to an active sulfenamide that covalently binds the pump. Because pumps must be newly synthesised before acid secretion returns, PPIs provide longer and more profound acid suppression than H2 antagonists, despite relatively short plasma half-lives.
Clinically, omeprazole promotes rapid symptom relief in gastro-oesophageal reflux disease (GORD/GERD), heals erosive oesophagitis, prevents NSAID-associated ulcers, and is a key component of Helicobacter pylori eradication regimens. It is available as delayed-release capsules/tablets and as OTC formulations for short courses in frequent heartburn. Optimal effect requires correct timing (generally 30–60 minutes before a meal) to match active proton pump recruitment.
Omeprazole is extensively hepatic-metabolised (CYP2C19>3A4) to inactive metabolites. Inter-individual variability is substantial; poor CYP2C19 metabolisers achieve higher exposure and more potent acid suppression. In older adults and hepatic impairment, exposure is increased. As with the entire PPI class, long-term use should be periodically reviewed to ensure the lowest effective dose and to confirm ongoing indication.
Combine therapy with lifestyle measures: weight loss if overweight, head-of-bed elevation, avoiding late or large meals, limiting alcohol and trigger foods (rich/fatty, peppermint, chocolate, coffee), and smoking cessation.
Omeprazole is generally well tolerated. Most adverse effects are mild and transient; long-term safety considerations are largely class-wide and based on observational data (association ≠ causation).
For many patients, benefits outweigh these potential risks; regular indication review and using the lowest effective dose mitigate long-term concerns.
For long-term users: attempt step-down to the lowest effective dose, switch to on-demand use for intermittent symptoms, or consider H2RA at night for nocturnal breakthrough where appropriate.
Key interactions involve gastric pH–dependent absorption, CYP2C19 metabolism, and effects on antiplatelet therapy.
Always provide a full list of medicines and supplements to your clinician and pharmacist; reassess interactions when starting or stopping therapy.
Missed dose: take when remembered unless it’s close to the next scheduled dose; if so, skip and resume the usual schedule. Do not double up.
Accidental double dose: usually low risk (headache, nausea, abdominal pain, dizziness). If unwell or symptomatic hypotension/persistent vomiting occurs, seek medical advice.
Large overdose: serious toxicity is uncommon; supportive care with attention to hydration, electrolytes, and symptom control is standard. Because omeprazole is highly protein bound and rapidly metabolised, dialysis is unlikely to help.
For recurrent heartburn despite OTC use, or for alarm symptoms at any time, seek medical evaluation rather than increasing the dose independently.
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