Omeprazole (INN) (IPA: ) is a proton pump inhibitor (brand names Antra® in Italy) used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and Zollinger-Ellison syndrome. It was first marketed by Astra Zeneca as the magnesium salt omeprazole magnesium under the trade names Losec and Prilosec, and 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.