Esomeprazole is a proton pump inhibitor (brand names Sompraz, Zoleri, Nexium, Lucen, Esopral; Axagon in Italy, Nexiam in Belgium and South Africa) developed and marketed by AstraZeneca which is used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome. Esomeprazole is the ''S''-enantiomer of omeprazole (marketed as Losec/Prilosec), and AstraZeneca claims improved efficacy of this single enantiomer product over the racemic mixture of omeprazole. However, this greater efficacy has been disputed, with some claiming it offers no benefit from its older form.
Esomeprazole is a proton pump inhibitor which reduces gastric acid secretion through inhibition of H+/K+-ATPase in gastric parietal cells. By inhibiting the functioning of this enzyme, the drug prevents formation of gastric acid.
Single 20-40 mg oral doses generally give rise to peak plasma esomeprazole concentrations of 0.5-1.0 mg/L within 1-4 hours, but after several days of once-daily administration these levels may increase by about 50%. A 30 minute intravenous infusion of a similar dose usually produces peak plasma levels on the order of 1-3 mg/L. The drug is rapidly cleared from the body, largely by urinary excretion of pharmacologically-inactive metabolites such as 5-hydroxymethylesomeprazole and 5-carboxyesomeprazole. Esomeprazole and its metabolites are analytically indistinguishable from omeprazole and the corresponding omeprazole metabolites unless chiral techniques are employed.
There has been some controversy about AstraZeneca's behaviour in creating, patenting and marketing of the drug. Esomeprazole's successful predecessor omeprazole is a mixture of two mirror-imaged molecules (esomeprazole which is the S-enantiomer, and R-omeprazole), and that the company was trying to "evergreen" its patent by patenting the pure esomeprazole and aggressively marketing to doctors that it is more effective than the mixture, claiming that omeprazole has no beneficial effects on the patient. However, in the acidic environment of the parietal cells both esomeprazole and omeprazole are converted to the same active drug which stops the gastric acid production.
Dr. Marcia Angell, former Editor-in-Chief of the New England Journal of Medicine, spoke at Harvard Medical School to a German magazine on August 16, 2007 and accused AstraZeneca's scientists of deceptively doctoring their comparative studies such that the difference to Omeprazole would look larger, providing a marketing advantage. For more information, see AstraZeneca's article.
Thomas A. Scully, head of the Federal Centers for Medicare and Medicaid services also criticized AstraZeneca for their aggressive marketing of Nexium. At a conference of the American Medical Association he went so far as to suggest that Astra was using the new drug to overcharge consumers and insurance companies. "You should be embarrassed if you prescribe Nexium," he claimed, "because you're screwing your patients and you're screwing the taxpayers."
An AstraZeneca sponsored study showed that 40 mg of esomeprazole provided more effective acid control than 40 mg of omeprazole.
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