Esomeprazole, the chief ingredient of Nexium, is a proton pump inhibitor [PPI] that reduces the acid secretion in the stomach. This greatly helps in reducing burping, abdominal pain and/or swelling, heartburn, nausea, gas. This medication is effective in the treatment of Gastroesophageal Reflux Disease [GERD], Dyspepsia, Peptic Ulcer Disease [PUD], and a rare ailment - Zollinger-Ellison Syndrome [ZES].