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rINN: Omeprazole
Other Names
bis(5-methoxy -2- [ [(4- methoxy -3,5- dimethyl -2- pyridinyl) methyl] sulfinyl] -1H- benzimidazole-1-yl), Losec ®, Prilosec ®
Pharmacological Information
Pharmacology Images
Omeprazole showing the two enantiomers. Esomeprazole is the top one (note the molecular form shown here has an extra hydrogen which would not make a stable molecule !)
Web information on Omeprazole
Metabolism & Interactions
Omeprazole can inhibit the metabolism of phenytoin, warfarin and diazepam
  • majority metabolised by CYP2C19 system forming hydroxy and desmethyl metabolites
  • reminder by CYP3A4 forming sulphone metabolite
Mechanism of Action
Proton pump via the achiral sulphenamide which is produced in the parietal cell.
Other Issues for Omeprazole
Produces inhibition for almost a full day even though plasma half life less than 2 hours
Relevant Clinical Literature
UK Guidance
Regulatory Literature
Other Literature
Other Wikis
Wikipedia on Omeprazole (Less technical, ? quality control)



The first and most popular world wide proton pump inhibitor. It is a racemic mixture and one enantiomer esomeprazole is still in patent.

Clinical Use





Group Clinical Issues


Group Contra-indications

Group Cautions and Interactions

  • There is now epidemiological evidence from two studies that all inhibit the actions of clopidogrel[1] when previously it was hoped the interaction was more specific. However clinically this interaction appears to be only significant for omeprazole and possibly esomeprazole.
  • There is to date an unexplained association between use in the frail institutional elderly and mortality. As absolute annual mortality increased from 26.6% to 33.3% this may be due to confounding.

Group Side effects

Special advice

Don't measure gastrin levels if a patient is on a PPI (or at least do not panic when you get the result back !).


see esomeprazole


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