H2-receptor antagonists are a class of medications that block the action of histamine at the H2 receptors in the stomach lining. By doing so, they reduce the production of stomach acid, which can help treat conditions like gastroesophageal reflux disease (GERD) and peptic ulcers. These drugs are often used to relieve symptoms such as heartburn and indigestion. Common examples include ranitidine and famotidine. They are generally well-tolerated, but like all medications, they may have side effects and should be used under the guidance of a healthcare professional.