H2-receptor antagonists are a class of medications that block the action of histamine on 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. Common examples of H2-receptor antagonists include ranitidine, famotidine, and cimetidine. These drugs are often available over-the-counter and are used to alleviate symptoms such as heartburn and indigestion. They are generally considered safe for short-term use, but long-term use should be monitored by a healthcare professional.