Proton-pump inhibitors (PPIs) are a class of medications that cause a profound and prolonged reduction of stomach acid production. They do so by irreversibly inhibiting the stomach's H+/K+ ATPase proton pump. They are the most potent inhibitors of acid secretion available. Proton-pump inhibitors have largely superseded the H2-receptor antagonists, a group of medications with similar effects but a different mode of action, and antacids. PPIs are among the most widely sold medications in the world. The class of proton-pump inhibitor medications is on the World Health Organization's List of Essential Medicines. Omeprazole is the specific listed example. Medical uses These medications are used in the treatment of many conditions, such as: Dyspepsia Peptic ulcer disease including after endoscopic treatment for bleeding As part of Helicobacter pylori eradication therapy Gastroesophageal reflux disease (GERD or GORD) including symptomatic endoscopy-negative reflux disease and associated laryngopharyngeal reflux causing laryngitis and chronic cough Barrett's esophagus Eosinophilic esophagitis Stress gastritis and ulcer prevention in critical care Gastrinomas and other conditions that cause hypersecretion of acid including Zollinger–Ellison syndrome (often 2–3x the regular dose is required) Specialty professional organizations recommend that people take the lowest effective PPI dose to achieve the desired therapeutic result when used to treat gastroesophageal reflux disease long-term. In the United States, the Food and Drug Administration (FDA) has advised that over-the-counter PPIs, such as Prilosec OTC, should be used no more than three 14-day treatment courses over one year. Despite their extensive use, the quality of the evidence supporting their use in some of these conditions is variable. The effectiveness of PPIs has not been demonstrated for every case. For example, although they reduce the incidence of esophageal adenocarcinoma in Barrett's oesophagus, they do not change the length affected. In addition, research in the UK has suggested that PPIs are not effective at treating persistent throat symptoms. Indications for stopping PPIs PPIs are often used longer than necessary. In about half of people who are hospitalized or seen at a primary care clinic there is no documented reason for their long-term use of PPIs. Some researchers believe that, given the little evidence of long-term effectiveness, the cost of the medication and the potential for harm means that clinicians should consider stopping PPIs in many people. After four weeks, if symptoms have resolved, the PPI may be stopped in those who were using them for heartburn, gastroesophageal reflux disease, or inflammation of the