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Proton pump inhibitors · Gastrointestinal

Omeprazole

Losec® · Prilosec®(brand names vary by market)

The proton pump inhibitor: profound acid suppression, and a deprescribing conversation waiting to happen.

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Illustration of Omeprazole as a capsuleOME

Also: tablet

Mechanism

Irreversibly inhibits the gastric H+/K+-ATPase in active parietal cells; effect outlasts its short plasma half-life because pumps must be resynthesized.

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Indications

  • GERD
  • Peptic ulcer disease and H. pylori regimens
  • NSAID gastroprotection in at-risk patients

Formulations

CapsuleTablet

Dosing concepts

Timing

30-60 minutes before the first meal: pumps must be active to be blocked.

Duration

Most indications are 4-8 weeks; indefinite PPI without an indication is one of the commonest drug-therapy problems in practice.

Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.

Pharmacokinetics

Bioavailability
~40% (first dose, rises with repeat dosing)
Half-life
~1 h (plasma) with ~24 h effect
Elimination
hepatic: CYP2C19 substrate and inhibitor
Play with these concepts in the PK Lab

Adverse effects

  • Headache, GI upsetcommon
  • Rebound acid hypersecretion on abrupt stopcommon
  • Long-term associations: B12 and magnesium deficiency, C. difficile, fracturesseriousAssociations, modest in absolute terms; the point is not to continue without an indication.

Contraindications & precautions

Contraindications

  • Concurrent rilpivirine

Precautions

  • Long-term use without a documented indication
  • Clopidogrel (2C19 activation: prefer pantoprazole where it matters)

Interactions

Monitoring

Ongoing indication, at every renewal

The monitoring here is editorial: should this continue?

Magnesium with long-term use if symptomatic

Hypomagnesemia is rare but real

Counselling points

  • Take it before breakfast, not at bedtime, unless told otherwise.
  • If we stop it after long use, expect a couple of weeks of rebound heartburn; it passes and does not mean you need it forever.

Clinical pearls

  • 'Why is this patient still on a PPI?' is the highest-yield question in any medication review.

References & review

  • Omeprazole product monograph (consult the current version for your market) (monograph)
  • Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)

Last reviewed 2026-08-15 · jurisdiction: global · drug information changes; verify against current references before practice use.

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