Famodin 20 mg contains Famotidine, which is a histamine-2 (H2) receptor antagonist. It works by reducing the amount of acid produced in the stomach. Famotidine is commonly used to treat conditions such as gastroesophageal reflux disease (GERD), peptic ulcers, and Zollinger-Ellison syndrome, a condition where the stomach produces too much acid. It is also used to prevent and treat heartburn and indigestion. Famotidine works by blocking histamine from binding to H2 receptors in the stomach lining, thereby decreasing acid secretion and promoting healing of ulcers and inflammation caused by excess stomach acid. It is typically taken orally in tablet form and can be taken with or without food. Common side effects may include headache, dizziness, or constipation. It is important to follow the prescribed dosage to ensure effectiveness and minimize side effects.