Esomeprazole is a proton pump inhibitor (brand name Nexium) developed and marketed in Sweden 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 (brand name Prilosec/Losec) also developed and marketed by AstraZeneca, and AstraZeneca claims improved efficacy of this single enantiomer product over the racemic mixture of omeprazole. Generic version of Esomeprazole is available in many countries made by Ranbaxy Laboratories of India. Ranbaxy's generic version of Esomeprazole is sold in several countries of Europe and in emerging markets like India, Peru,Ecuador, Carribean Islands, Nigeria, Africa, Srilanka, Cambodia and Myanmar under the brand name Raciper. Esomeprazole is a proton pump inhibitor which reduces acid secretion through inhibition of ATPase in gastric parietal cells.