Omeprazole is a proton pump inhibitor used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome. It was first marketed by AstraZeneca as the magnesium salt omeprazole magnesium under the trade names Losec and Prilosec, and after the AstraZeneca patent expired it is now also available from generic manufacturers under various trade names. Omeprazole is one of the most widely prescribed drugs internationally and is available over the counter in some countries.

Omeprazole (and esomeprazole) is a proton pump inhibitor which reduces gastric acid secretion through inhibition of H+/K+-ATPase in gastric parietal cells. The inhibition of this enzyme the drug prevents formation of gastric acid.

Faced with the loss of patent protection and competition from generic manufacturers, AstraZeneca developed, launched, and heavily marketed esomeprazole (Nexium), a single enantiomer form of the racemic mixture of omeprazole. The two drugs are AstraZeneca most profitable with $1.652 billion in sales for Losec and Prilosec and $4.633 billion in sales for Nexium. AstraZeneca claims that esomeprazole provides improved efficacy, in terms of stomach acid control, over racemic omeprazole. The study usually cited by AstraZeneca to support its claims is of doubtful study power. Lind et al. (2004) compared esomeprazole to omeprazole in a study of only 36 GERD patients. It is noted that this study was financially supported by AstraZeneca itself.

Formal Chemical Name (IUPAC)
5-methoxy-2-((4-methoxy-3,5-dimethylpyridin-2-yl)methylsulfinyl)-1H-benzo[d]imidazole

References

http://en.wikipedia.org/wiki/Omeprazole

http://en.wikipedia.org/wiki/Esomeprazole